His ex fianc�e is trying to talk to him...?

Iv been talking to this guy for about 4 weeks now. Things are amazing between us. He is in the navy, and I am in college. Well he use to be engaged. She called it off. He helped her move out and that was the end of that. Then he went out on deployment for 8 months. Well shortly after we started talking he added me on facebook, and me being the jealous nosey girl that I am ( i do this with all guys i date)...i went through some of his post (werent that many) and saw that she wrote on his wall occasionally (these were from like august or so. We didnt even know each other then) it was just chit chat and he seemed to be very short with her. Well today he went out to sea and wont be back til thursday. I got on facebook today and he had posted something so i went to his page... and i notice she had wrote something on his wall and commented on his profile pic. the wall post was random it said "yay my fool"... he replied "lol what". Now i know im probably reading way too much into this, but iv always had jealousy issues. Not to mention that I cant talk to him til thursday and since she is his ex fianc�e I feel she already is ahead of me. What should I do? I really like this guy and he really likes me. He has given me no reason not to trust him. He is amazing. I just feel vulnerable since we arent together and feel i have to keep my guard up for anything that may get in the way. We text all day everyday, talk on the phone, we skype, he text me every morning "good morning baby"... and he text me early this morning before he left out to sea. The only reason we arent official is cuz we are waiting until I come home in 3 weeks so he can ask in person. should I just chill out?