first time having sex and didnt use a condom, always have irregular periods, light bleeding now

Ok I know extremley stupid. I'm 24 and have been waiting to have sex until I found someone worth sharing it with, but I got really really drunk one night and my friend came home from the bar with me, and I guess one thing lead to another. I was so drunk I don't even remember most of it. Just bits and peices. Well anyway that was 2 weeks ago, now I've been having lower abd discomfort, bloating, lower back pain, my fav foods don't sound good but things I didn't like before do, and I just started light and I meave very light bleed that's bright red. I have very irregular periods, I can go 3 to 6 months in between. Pls give me some advise I'm absolutley freaking out! Thanks