Hurt during anal

Hey guys so my boyfriend was going doggy style on me last night and then switched up and went for anal. We were not prepared at all. I know he got a bit of spit on there before going in and I could tell what was going on but I trusted him and let him go for it. Bad idea. He went in so quick (literally with the same speed and power as he would during vaginal) that I collapsed screaming for it to stop. I had to lay there for a while in pain. The pain faded so he went back to our typical vaginal intercourse and finished and we went our separate ways home. After I got home I noticed I was bleeding. Not much but enough to scare the crap out of me. I went to bed hoping it would stop. I woke up today and it hurts. Like aches. Every time I sit up or do so kind of movement that affects my butt then I gasp from the pain. My SO feels so bad and keeps telling me he's sorry and checking up with me over the phone. Help me out please. Did he tear something? When will the pain go away? Any similar stories that happened to you? How do I go forward and prepare for next time? I'll take anything.