Why don't you cultivate rich and meaningful friendships with all these men? Make it clear to them that you really value them as people and that you're interested in becoming part of their lives and having them in your life, but that you need time to know whether your futures together will be long term romantic or not.

If they're great guys, they will value you as a friend even if the romantic love doesn't work out.

And if you do it this way, at some point you will KNOW which (if any) of these men you want to spend your life with.