Quite long... But any advice/comments on how I can make myself feel better?

Last summer, when I was with my (now ex) boyfriend we were together in his bedroom and we're having sex. Knowing I didnt want to, he asked if we could try anal.  Neither of us had done it before, and he said he wanted to try something new, but I hate the sound of it (my personal opinion, I don't judge people who enjoy it).  I told him no, that I didn't want to and he kept pestering and asking.  I repeatedly said no and asked him to drop the subject and enjoy the normal sex.  Instead of forgetting and carrying on, he stopped and turned away from me and wouldn't talk to me.  I asked him what was wrong and he ignored me.  I wanted to go home by this point, but my phone was dead and he lives in a different town to me, so I had to stay at his.  I begged and begged for him to talk to me or at least tell me what was wrong, but he wouldn't speak.  I asked him if he was going to ignore me for the rest of the night and he looked at me then away again.  I asked what I could do to make him talk to me, and he replied "you know what...".  Hearing this my stomach flipped.  I had to choose to either stay with him for the rest of the day in utter silence or otherwise uncomfortable circumstances or give in to him and do something I really didn't want to do.  All I could reply was "fine...", and he positioned me and did it.  I silently cried the whole  time, from pain and because I didn't want to do it and was wishing it would be over.  When he finished, he laughed at my puffy face, from where I'd been crying, and asked if we could do it again sometime.  I know he didn't exactly force me, seeing as in the end I did in a way give consent, but I just felt so violated.  I feel so ashamed with myself that I gave in to him and put myself through it, but I couldn't go through with him treating me as if I wasn't there.  I wish I had been stronger.