Question about being cheated on and your risks of cheating...?

Ive been cheated on by my first true love, and it hurt but i know i would never do that to someone because of i know what it feels like. My bf has been cheated on by the girls he cared about also, and is hurt by his previous relationship because he found out accidentaly, that she had been screwing some other guy numerous times. So now he is sort of tainted in that fact. BUT he tends to stare at other women when we are together...last night he stared at the hostess trying to catch her attention, and she was eyeing him back. He even would not pay attention to conversations at the table (i was with his family) and then limp in at the end AFTER he stared at her as she walked by. It was so obvious. So im confused. He also tends to like attention and has a big ego...I dont think he would ever cheat on me, but I do think he would talk to other girls and keep contacts with people that are interested in him... and I dont agree with that. He adds girls on his myspace and always has messages in his inbox...does that mean he just likes to know he is wanted...but thats all? I just dont know when a red flag is there that I should be concerned? I just dont want to get screwed over...