This is a tough predicament! When I personally have that problem, I transform it from a problem into a poly family. Of course, not everyone is open to the concepts of polyamory (to openly love more than one person), so that could be unrealistic. You just never know, though....

OK, back to reality and the vanilla world. If you are dealing with people that are not open to the alternative of polyamory, you must first do some soul searching within yourself. What does love mean to you? Is it passion, security, soulmates or simply unabated sexual attraction? What is the level with each? Look at each one and before you make rash decisions, try to realistically imagine the rest of your life with each one of them. Do you feel different with each one? Be honest with yourself and try to look at the larger picture with each. Ask yourself if you would spend the rest of your life with either one. Whatever you do, PLEASE do not sneak around on one and see the other. That would cause more hurt than simply choosing one and letting the other go. You can't, in fairness, keep them both on a string, so there's going to be some difficult things to face. Probably the most difficult thing is going to be to try to make your feelings known to both so that there's no lying, and try to come to terms with this in whatever way the Gods have destined. I can't tell you what to do, but I can advise you of how to do it: Honestly, openly, and sincerely. Yes, it could cause pain for someone, possibly even some heartbreak. I promise you, though, if you hold back your feelings for fear of hurting one of them, you will hurt him, and yourself more.