Girl, please. It’s not controlling to demand common decency. Ask him if he wants to see other people. If the answer is yes, then you do the same. If he says he wants to be with just you, don’t be afraid to call him out when he behaves disrespectfully. Take it from someone who’s been there: these kinds of guys don’t change. But there is someone out there who will have eyes for only you.
So, funny story. Before Vegeta and I got together, he overheard me doing exactly what I told you to do with Yamcha. I told him if he wanted to break up, that was fine, but as long as we were together, if I caught him looking at other women again I’d pluck his eyeballs out and wear them as earrings. Vegeta later confessed that was the moment he fell in love with me (not exactly the phrase he used, but it would take too long to explain the Saiyan equivalent).
Bottom line: stick to your guns, be strong, and demand the respect you deserve. It’ll pay off in the end.