Boyfriend problems

So recently my boyfriend & I had sex and he's been acting strange ever since we did it. So today he comes to me & says that he's been having "red bumps" on his penis. He had the nerve to ask me "do you have anything He should know about? " (but mind you, he's the only dude I've ever slept with! Like EVER ! ) LOL so I was like huhhh? "What do I have ? Nothing !" so then I started thinking like wait a minute, because he used to tell me stories about how him and his ex girlfriends almost had sex before he met me & stuff so I was like whatever you have you most definitely didn't get from me.

So then I started to ask him if he's been cheating on me. Whatever whatever he says no. But I didn't believe that because I mean where else would he be getting these bumps & rashes from !but anyways I was more mad at the fact that he didn't think to tell me this wasn't the first time he had seen it on his penis ! So we looked up his symptoms & turned out he had a thingy called (I forgot what it's called ) but it's nothing transmittable.

So overall I'm still mad at him because he didn't tell me ! I also think he's cheating & he accused me of having some typaa infection. Any advice? Ughhh☹️