My Dad won't accept I'm bi

Look I need some help, I'm a (19yrs) old man and I live with my dad! The other day we got into an argument for like 3 hours, now admittedly he was trying to joke with me but we went back and forth on how if I'm with a man I'm gay not bi and if I'm with a woman I'm straight not bi! He says it's just a cop out and that I'm weird for being fine with being called bisexual and not gay! Being gay would mean I have no attraction to women which isn't true(matter of fact I prefer girls), then goes off with this schtick about my gf or bf not being able to trust me at the thought of me being bi, which I could understand but if I'm with HER, I'm with HER. If I'm with HIM, I'm with HIM. But ofc he repents with, "Well that means your a cheater then!" Dude, what the hell?! ANYWAY, if anyone has advice to help me out here, cause my father won't listen to me. Not I need his acceptance just maybe get him to back off.