IM IN A RELATIONSHIP FOR OVER 7 YRS.JUST GOT ENGAGED BUT NOT SURE OF MY SEXUALITY AND HIS.?

Well i been with this guy for over 7 yrs.He finally propose,and i thought that this is what i really wanted.But know im really thinking about it.The thing is that i notice that he likes to see trans gender porn!I mean,im cool about him watching porn.i really don't mind,but why not girl on girl action or something more normal?To make it worst i have curiosity in being with a girl also!!i thought in suggesting on going on a swingers club or to have a night out without each other,im so confuse on what to do or think.i haven't talked to him about it like that but i don't think his gay.Maybe "by" or just curious.should i give him the option on trying it?and give my self the chance too?i don't want to ofend him or seem old fashion.i really need suggestions...PLEASE HELP...whaaaaat should i do?