Smelly penis???

So I started dating this guy ive known for a long time. real down to earth person. All the good qualities. When I decided I was ready to take it there I smelled something that didn’t seem normal. It wasn’t really bad but the odor was there. It immediately turned me off and I started looking for excuses to actually stop and not embarrass him. Long story short I said my stomach hurts really bad and went to the bathroom until the mood changed.

Now my question is has anyone ever smelled an odor on a guy and what causes it?!?