You have to ask yourself if he cheats now will he cheat on me and the answer is probably yes. I know that when you are feeling this strong for someone you dont want to let go, but be strong and go out and enjoy yourself there are plenty of people out there. Go and find yourself someone who will feel the same as you. Love is something that develops in a relationship and the more committed you are to each other the stronger it will become. A relationship built on lies and cheating is doomed from the start because trust will never be there. I am a firm believer in you can love more than one person, maybe differently but a relationship between two people is about trust and committment, without either it will surely end in tears.