How we make out and cuddle and stuff without him getting “blue balls”?

Ok so my ex once told me that I have him blue balls for the first 4 months we were together and I felt really bad. And now my new bf and I make out and cuddle but I don’t want to have sex until I’m sure that we’re in love. So when he does try I just tell him we’re moving to fast and he’s really ok and respectful of it but at the same time I really don’t want to make him go through that pain. Idk how sometimes they get them and sometimes they don’t. Any tips, opinions, advice, info on this would be great, thanks!