Confused... Not sure if anyone can help

So a couple of months ago I slept with a guy and he was on the bigger side of things. A couple days after he messaged me saying he has small white bumps on the head of his penis and he questioned if I was telling the truth about being clean and tested (I was telling the truth). I told him that there was a bit of friction and that could be the reason and we both got tested again and we both come back clean like I knew I would.

A few months had past and we crossed paths again. A little while after talking we ended up sleeping with each other again and it happened again... it is really frustrating because I don't know what it is or what it could be. I don't like the idea of him thinking I am lying or anything.

I have no issues or symptoms or anything after having sex with him so it's just one sided. I'm going to book an appointment and talk to my doctor about it but I am one to over think so thought I would come here for some advice. It only ever happens with him and none of my other partners have got this.

Has this ever happened to anyone else? Or heard of it?

Any help would be appreciated x