<human>: So, I've been dating this guy for about 6 months. We're in love, and I do trust him so much and things are going extremely well. 

The only thing, is just tonight I was messaging a friend on his facebook when I accidentally pressed the back button and it brought me to a list of all his recent facebook messages. One was from a girl, and all I could see was her recent message of " ;) ;) " and it made me sick to my stomach. I'm telling myself I'm wayyyy over reacting. 

Of course, I didn't look into it any further, or even ask him about it. Like I said, I trust him and love him dearly, but is this feeling of jealousy or suspiciousness normal? He noticed I started acting quiet and when he asked me what was wrong, I played it off like I was fine. He was really concerned and apparently I'm not good at hiding my feelings. 

Anyway, sorry for rambling, I just don't like this part of being a girlfriend and would love to know how to overcome that.

Provide a brief overview of the text.
<bot>: Saw brief and potentially innocent message from girl on boyfriends facebook and I got extremely suspicious. How do I stop this??