Should I be worried about my boyfriend?? Please help?

[xoxoox0]

My boyfriend and I have been together for almost a year and a half.
We have always had a great relationship and have never broken up. He has given me no reason not to trust him in the entire time I've known him.

He picked me up emotionally after my last boyfriend (who cheated on me with 9 different women)
and has earned my trust (for the most part)

He lives 2 hours away now and goes to college. He lives in a house with his brother & his brothers girlfriend. (I've met his brother and his brothers girlfriend)
So even though he does go out, hes not doing anything crazy from what I know. His brother and his brothers girlfriend are very mellow and even though her and I arent close, I know she would let me know if he was bring other girls into their home.His brother also made it very clear to me that men who come from their household do not cheat on their women and respect them. Which has as far as I know been true.

Him and I have been making a 2 hour distance work for 6 months. We see each other on the weekends every week and if not, every 2 weeks. He comes down and stays for months at a time on break and during the summer. His parents also live in my town so he's here quite often.

Lately I've been having some trust issues because he added a girl from new school (college) on Facebook. He added her when we had just made up from a long fight we had over a weekend.
Shes the only girl he's added from his new school and all the rest are the players on his football team.
I don't know whether I'm just insecure and paranoid because of how things ended with my last boyfriend or if theres something going on with her.

I'm scared he is going to meet someone new or leave me for this girl he added..
I just think its weird, why does he only have her from school? Could she just be a new friend hes made? How do I know this wont turn into something more? THIS GIRL USE TO GO MY HIGH SCHOOL (where I go now) I'm a senior and will be graduating in May.

Right after he added her though, about 3 or 4 hours later he wrote on my Facebook wall telling me how much he loved me and how lucky he is. He spilled his heart out on my Facebook wall which isnt usual for him..
It says he's in a relationship with me on Facebook so this girl is fully aware. I'm just concerend and I'm scared to ask him because we just got out of a long and exhausting fight. I dont wanna start another one.

What should I do?