Most Helpful Guy
Jealousy and loss of trust perhaps.
Most Helpful Girl
Well here is the thing, since his friend talked to you your ex is now trying to see if you are being happy without him now. He is kind of just keeping tabs on you but at the same time seems like he may want to see if you and his friend become more than friends. In the end I think you need to just move on and ignore that he is looking at your stuff because if you focus on that you will either make yourself sad or mad at the situation.