First of all you were/are not stupid do not think you are no matter what happened.

Not everyone remembers everything that is normal. There was so much going on right at that moment, your brain has focused on the important things, and let a few things slide. You can't be expected to remember everything.

You stopped struggling, so what. That does not diminish what happened to you in the least bit. It in no way means that you gave consent. At the point you say you quit, he had you pinned there was no way for you to get away, it is possible that if you had continued to struggle it would have been worse for you, he might have decided to beat you, or try to make it hurt worse.

I think you did the right thing, it could have been worse for you if you had continued to struggle. You could not have stopped it no matter what you had done. He was apparently stronger than you, so you could not have gotten away no matter how hard you struggled.

I replay the events leading up to my rape, and I keep saying if I had been smarter, I should have known better than to go with him. I really did not like him the first time I met him, so why did I agree to go to his apartment anyway? I remind myself that we were introduced by a mutual friend, someone I trusted. If she trusted him, then why shouldn't I trust him? But, then I let him fix me a drink without watching him, how could I be that stupid? Who would have thought about him drugging me?

We can be so critical of ourselves when bad things happen. I had a car wreck a few years ago, and I still keep saying that if only I had took a different street, or had driven slower, or faster or actually stopped at the previous stop sign, instead of a rolling stop. So many what if's, if all the what if's had happened the world would stop spinning. You can not let the what if's make you think that something else could have happened.

Don't think you are stupid because you got in a bad situation, I don't know the specifics of what happened that led up to your attack, but I really doubt that you could have known that something bad was going to happen. I doubt that you could have known anything that would have led you to make another choice. NO matter what your mind tells you, don't believe that you were stupid.

So many of us have gaps in our memory of rape. I've heard it from many people who were raped or molested. I have those gaps in my memory too. It's not because you're stupid, so please stop thinking that about yourself. You have to learn to be kind to yourself. Getting raped is awful - you deserve a break from awful. If someone else told you they'd been raped, and they couldn't remember every second of their rape, would you call them stupid? If the answer is no, then why be mean and judgmental to yourself when you would be kind to someone else in the same situation? You do not deserve the blame when someone does something bad to you. The person who did the bad thing deserves the blame! Get mad at him, not at yourself. You deserve support, not blame.
I've thought about this a lot, why we blame ourselves, get angry with ourselves, call ourselves stupid, etc.after rape. I think there are at least 2 reasons. For one thing, when we are really small, if we do something wrong and we get punished, it sinks in very deep as a lesson; do something wrong and you get punished. Then later on, if we experience something punishing, we turn that lesson around and think we must have done something bad or we wouldn't have gotten punished. But that's just not true. The reason we classify things like rape as a serious crime, and try to catch these people and put them in prison is because they commit abnormal acts that violate us, and we don't want people like that running around.
The second reason we blame ourselves is that it is very hard for us to admit that we were in a situation we had no control over. That is very depressing, and it goes against everything we want to believe about living in this world. We'd rather believe that if we did something different, we could have prevented it, even when that isn't true.
As for not being able to remember every detail - many of us have those gaps in our memory of rape. It's because our brains decided that the best idea was to take a break since we couldn't stand what was going on and couldn't stop it. It may be disconcerting, but your brain was just trying to shield you. It's called dissociation, and it's a reaction to stress. Don't beat yourself up about it, please. I did the same thing at various points when I was raped. I can't remember how I got from the living room to the bedroom, and I can't remember how I lost my clothes, or how I got from the foot of the bed to lying on the bed. I'm actually grateful that I lost some of those memories - what I do remember was bad enough.
As to why you stopped screaming and struggling - probably you stopped because it wasn't working, and it was exhausting you. I screamed so hard during an assault that I passed out, which made me very vulnerable - not a good thing. You force out your breath as you scream, which deprives your brain of oxygen. If you keep it up long enough, you pass out. You probably realized that you were making yourself weaker, and it wasn't working, or else you realized you were making the rapist angry, which could have made things worse for you.
You couldn't have stopped it. You tried. You're not stupid. The rapist was stronger. Please,please stop blaming yourself. This didn't happen because of anything you did, and it didn't happen because of anything you didn't do. The bleak and simple truth is that it happened because somebody stronger than you wanted to rape you. When somebody pins you even if you're screaming and struggling, it means that screaming and struggling wasn't working. We don't want to believe that someone could deprive us of our freedom and hurt us, so we struggle against the idea and try to tell ourselves that we could have stopped it, but we couldn't. The rape happened. Now the task at hand is to seek inspiration, information and support to balance out the horrible experience of getting raped. You can go to the RAINN.org website for more info and local referrals for counseling and advocacy. You've found this website where everyone is here for the same reason - to give and seek support. You have to be extra nice to yourself, too, after something awful like this happens. We're all on your side. Please do something nice for yourself this month when you remember your rape. Let yourself know that you are in control now, and that you're going to be good to yourself.