cheating, stds, bad relationships

Okay this is gonna be a weird one for you guys... so recently my now ex boyfriend accused me of giving him chlamydia because I slept with another guy while we weren't dating. (We had previously dated for a year and then broke up for ten months and then started talking again but moving on) I feel kind of attacked and angry because while we weren't together he admitted to sleeping around with about 30 other girls(idk about w or w/out protection) but since I slept w one other guy this whole thing is my fault? The reason for us breaking up first off was because I found out he had been cheating and didn't tell me until after he came home from college and slept w me🙄 I'm getting tested myself this next week bc I was on my period and couldn't when he told me. I just need some advice on how I should handle all of this and comfort to not feel stupid and guilty and lonely and lost. Sorry if it's too choppy or not understandable I just really needed to get it out.