I Tried Anal Sex For The First Time Tonight With

I tried anal sex for the first time tonight with my boyfriend. It hurt, like I knew it would, but he said it'd feel better once I relaxed and got used to it. We only did it for a few minutes because it hurt too much for me. I've already noticed I've gotten hemmoroids and a little blood in my stool, but now my stomach won't stop churning and feeling sick. I keep going to the restroom to take another BM, thinking it'll help, but it hasn't. Should there be any concern?
P.S. We also went out for Mexican food afterwards so I'm not sure which one is bothering my stomach...