Could I have an STD??

So I think I could have an STD. I’m not experiencing any symptoms but my boyfriend has two red lines on his penis(horizontally) and he said it hurt really bad when we’d have sex. But we’ve been waiting and it’s been looking and feeling a lot better, it just feels kind of chapped. We tried to have sex again but it started hurting afterwards again. I was tested in December and I was clean and he got tested last month. Do you think it’s possible that one of us contracted it in late December/early January and it didn’t show up in the tests? We also used a new lube the day before he started experiencing symptoms and he says he didn’t wash it off properly and that he’s probably allergic to it. What do y’all think?