Sti or irritated???

While me and my first love wasn't together I gave someone else a blow job and had sex with a Condom! I found out he was having sex and eating another girl out while I just had my baby and he been doing it for a month or two we just got back together let's say a month ago and it's been just us we had sex without Condom and after his dick been irritated I don't know why I had got checked after I gave the other person a blow Job and everything came back negative ....his penis has been irritated for 2 weeks now he also uses exfoliating soap so I don't know if it's me or him