The way I see it, you have two options:
1.) Tell him how you feel and risk losing the friendship if he doesn't feel the same way, or
2.) Keep it all inside and regret it later with the "what if's" of what could have happened.
Chances are, especially since he used to like you and he is hot/cold, that he still likes you too. He just doesn't know how you feel and is afraid of your reaction.
It's a tough situation and it's easier said than done, but I say go for it! You could always try doing it in a casual setting and then pretend it was a joke if he's not into it!
It's generally thought that a male and female cannot be friends if they have any sort of "other" feelings towards each other. Turning long term friends into partners is a bad idea, turning short term friends into partners is a good idea.
But always remember turning partners into friends is impossible... if you value your friendship with this person, and can't live without it. Never cross the line
I think it is more important to let things evolve naturally with men with whom you are friends and would like something more. My parents were just friends first and it just evolved for them. Don't let your possible interest in your friend deter you from dating or influence you to make wrong decisions. Just be honest with your feelings, flirt appropriately, and enjoy their company. That is what friends do.
Sometimes you have just gotta take the risk.
But I tend to find that when I want to take a risk I will know that its worth it - cause everything has a time and a place - if that makes sense to everybody reading. Taking that risk will not necessarily get you him or what you want outa the situation, but it may help as a process of eliminating and evaluating what you really want in the end.
First you need to decide whether you do really want to be with this guy, because telling him how you feel does risk the friendship ending. Could you face still being friends with him if he rejected you or you got together and it didn't go well?
If you really, really can't bear just being friends with him then your just going to have to bite the bullet and tell him exactly how you feel. Invite him over one night or out somewhere, try not drinking as this might lead him into doing something he'll regret and then hurting you. Just spill your guts to him tell him your finding it too hard being just friends & keep your fingers crossed!! Good luck!
If the idea of telling him flat-out how you feel is a bit full on for you why don't you try flirting gently with him, flattering him and batting your eyelashes etc and see how he responds?
Just be careful. I agree with Irrose. Let it evolve naturally, and see where it ends up, but sometimes having a close friendship lead into a relationship, you do run the risk of ruining what you had with this person. My friend started dating her best friend, and realised they didnt get along, and when they broke up, they didnt speak for over 2 years, before she sat down and said "look this is stupid, we were realy good friends before this relationship, dont ruin what we had" they are just friends now, who only contact eachother once in a blue moon, which I guess is better than nothing.
I say go for it! Wish I had and that is far worse!
You don't have to pounce and say 'how about it tiger?', but it does sound to me as if he is very interested and perhaps afraid of possible rejection.
A case of slowly and surely wins the race....