I think you are asking the right questions. The jealousy is telling you something about how you feel deep down. Maybe you worry about losing him and the pain that would cause? So you protect yourself by being cold to him?
You are want more time with him and you felt less important because he is donating more time to other things (and people). How would you have felt if he chose to have a new hobby instead of seeing another girl?
Do you feel that on some instinctual level that if he sees these women that he will like you less?
I think this has a potential to be a growth opportunity.