Hi there,
This is tough, because you realize that you love him, but honestly I think you are being used.
The fact that you have broken up several times before is also telling, but I'm not sure if either of you dated others during your past times apart.
In anycase, I would consider several things:
1) Saying he is emotionally unavailable is probably a sign that he is not interested (hmmm...some similarities to my own post...).
2) He is using you by remaining friends in case something else doesn't work out - or at least that is your suspicion. You have been together on and off for a couple of years; and I would say trust your intuition.
3) You have broken up several times before; do you really want to remain on this emotional roller coaster?
4) Have you considered the possibility that you are in love with the idea of staying in a relationship that is comfortable and familiar, as opposed to REALLY being in love with him. Not saying that you are, but it is worth considering.
My advice is to leave the relationship, take the time to heal, and then get out there and meet new people. It will be very painful in the beginning, but could play massive dividens down the road. at 24 you don't need this strtess in your life - wait until you are my age
Best of luck with your decision.
Closeau