I liked a guy since a long time but finally when he proposed I said a no to him... I was quite convinced by then that I don't really love him and I am still sure that I don't love him its just attraction but when he talks about other girls or hangs out with other girls I feel jealous.. I don't know what I actually feel for him

You said no,so presumably you don't feel you want to be with him.

If you feel jealous when he's around other girls,it could be that you like the fact that he's 'into you'even though you don't want to date him.

this occur naturally that when you lose something you want it back.
cause you don't appreciate it's value unless it's lost. Or when somebody in your life care about you then suddenly he go, you feel that there is something missing in your life (that guy was filling it)so you need to get it back,soit's not because you like him!
so I think you don't love him, you can get over it just give yourself time and try not think about this...
and also try not to hurt him cause if he felt you need him again you will ruin his life.
hope it helps you...

You have to give it time ;)