Anxiety Support Group
Anxiety is a physical condition marked by intense and persistent feelings of distress, fear, angst or dread. General anxiety caused by routine day-to-day stresses usually passes quickly and is experienced by almost everyone at one time or another. However, such feelings that linger over time and are very difficult to cope with, and which lack a clear cause, may indicate...
The more important question, is in regards to what you wrote later, "I only noticed recently how i felt so upset about it"
I think it is very important that you listen to how you feel, express it and talk through it with people you trust.
Consent ends when one person says stop. It may have been unintentional? It may have been deliberate? I suggest reaching out to the rape crisis hotline and seeking advice there.
But, I will also add that if you are comfortable with this person that you consider if talking to him about this experience would be helpful. Tell him how you felt with the experience and set (re-set?) the boundaries for expectations, and if he can't accept that or is otherwise the least bit unsympathetic, unapologetic, or uncaring about it then cut him off. Or just cut him off already without talking to him about it, since his ignoring a statement of "stop" ends things in and of itself.
Going anal without consent and continuing after explicit rejection of it, is not acceptable under the category of "playful experimentation that just didn't work for one person." Anal is it's own category, and just because regular intercourse may be acceptable doesn't mean anal will be. In the same way that just because oral may be acceptable, doesn't mean that intercourse is. So even though a person had said yes to one form of sex, doesn't mean that all others are a go. Consent must be constantly given throughout the interaction (and things like "safe words" must be respected for folks that enjoy (and mutually agree to) blurring the lines intentionally.)
You've taken the important first step in writing it out.
However, asking people's opinions about intimate experiences on a public forum is not the best way to find answers.
Circumstances blurred lines does NOT mean consent in any way, shape, or form.
That being said, you can not change what happened. What you can do, however, is change the way you act, react, respond, and that will change how the other person reacts, responds. It can get worse before it gets better. You are responsible for what you say, do, react, and respond. You are NOT responsible for what others say, do, react, and respond.
I would suggest writing it out in a private journal and not on a public forum.