Wow - I know exactly how you feel. My husband and I had our first doctors appointment on 9-23 and got our first picture of our baby. We were floating on air, we were so excited and couldn't believe we were able to get pregnant so soon and that we were going to be parents!! Two days later, my world came crashing down. Sunday night before going to bed, I started to miscarry the baby. The whole night seemed like a blur. We went to the ER that night and were told that they couldn't find a heart beat. Words can't explain the devistation we felt. After going to the doctors the next day, we scheduled the D&C for Tuesday. I just can't believe how similar the timing of our situations are.
I think you hurt so much because becoming a mom is one of the most amazing/scary/inredible/etc. experiences we will ever have. We find out that we have a little one growing inside of us and we fill with emotions. In our cases especially, you just get used to the feeling and it was ripped away from us.
Everything you say you are feeling, I am feeling too. My husband and I can't wait to try again, but we are also scared and don't want to have to go through it again either. I may be a little older than you :) but I know what you are going through.
I hope your boyfriend will open up to you, but everyone grieves differently. It took my husband a couple days to really break down and tell me how he was feeling. But when it happened, it made us even closer.
It has been 1 week since we lost our baby, and sometimes it feels like the worst week ever. But then I have to remind my self that we've had our little angel, safe and sound in heaven, watching over us for a week now :)
I hope things get easier and I am here for you if you ever want to talk.

I'm also 20 years old and just found out I was pregnant 4 days before I miscarried. I don't know how other people would feel about being pregnant only this short amount of time, but I was completely devastated and still am 4 months later. You're definitely not alone in this. I've also had to deal with people not understanding why I'm so upset after only a short time, but I know I'm a mother rather they consider me one or not. I'm very sorry for your loss, but just know you're not the only one, and although we'll never forget, someday it will get easier. I try to just look forward to the future when I can have another child, and I know the one I lost will watch over the next one.

i know exactly how you feel. it doesnt matter if you knew for nine months or a day, it was and is still your baby. it's okay to feel the way you do; completely normal. it's stages of grief. it's been seven months since my mc and i am still upset and mad.

my opinion about your boyfriend:
i thought the same thing about my bf. that he'd be happy. but from the moment i told him i saw the hurt in his face then i felt bad because i caused that hurt. three months after i told him he told me he was still depressed and was thinking about it constantly. I wanna say just give him his space. he needs that to grieve. i think all men are like that. i love my boyfriend so much though because everytime i cried, he held me. every time i needed or wanted to talk about the baby, he listened.
just give him some space. try talking to him little by little. that's how i did it. it started with small tiny just little comments and now we can have full out conversations about our baby..it's hard but we manage.

but yes, your hurt after only four days is normal and i dont want to say this to be mean but the pain will get worse before it gets better. as i said it's been seven months since mine and i still lay in bed in cry.
i hope this helped; i'm so sorry about your loss and i'm here if you ever or just want to talk