Like XP said your in a loose, loose situation, tell the dude too much he'll start to think your over emotional keep it to yourself and he'll think your the ICE QUEEN (muhahahaha)

Just wait and see, if he sticks around while your still keeping things bottled up then I'm sure he'll stick around for the ugly truth (that I assume your keeping bottled up)

. Don't start pouring your heart out all at once, think of it as opening a tap, let the water run out slowly then, let it all out. whatever you do don't feel guilty for not opening up to him, that'll just make things worse.