Stuck in a pickle

So it's a circle of coworkers and we are all hang out buddies. I was a new girl so a few guys showed interest in me. I took a liking to two in particular, we'll all them Justin and Frank. As time went on I begin to realize that Justin was just a fuckboi and me and Frank had a lot more in common so we naturally grew closer. Ok. So one night we all go out and Frank decides not to come last minute (I only went because he said he would be there) so I decide to make the most of it with everybody else there. Well me and Justin were laughing and having a good time and he asked if I wanted to go to a mutual friend's house. I agreed. He drove so on the way there we were drunk and begin making out. It was disgusting. I was turned off. And We didn't have sex because he didn't have a condom. Plus his penis was the size of my pinky. He told me that I "better not" say anything to anybody and I told him not to worry because I definitely wasn't. We never spoke about it again and act like nothing ever happened. Plus he begin behaving like a jerk and telling me I can't speak to him in public so I definitely paid him no mind. Fast forward a month later we all go out and Frank and I click so well. We ended up having so much fun and ended up having sex that night. We started a relationship and Frank kept trying to find or if something was going on between us. We never said anything about our relationship to anybody really. Well fast forward months later, we are out for Frank's birthday and Justin is telling Frank, the guy I'm dating, that we had sex and I was all over him. So Frank confronts me about it but doesn't know who to believe. So he's mad, wondering if I'm a slut and jumping from man to man. Then keeps telling me how Justin is a whore and he's disgusted I would even talk to him because he had more respect for me than that. So this goes on for like 4 days of him not talking to me until he finally says that he's not going to trust Justin because he can tell that he always liked me anyways. He didn't want me to say anything to Justin but here it is 2 years later and everytime they are around each other, I feel uncomfortable because I just feel like Justin is going to say something inappropriate to Frank again and I think I might lose my relationship since Justin is a hater. And I don't want to bring it up to him.