Abnormal jealousy or being cautious?

My hubby and I have been married for a year and a half, have a 1 y/o and we love each other. Twice last year I caught him flirting (through text a few months in between) to two different girls. I confronted him and we talked it out.. But tonight I mentioned one of their names by happenstance in talking about one of my friends with the same name, and he perked up with a "who?". It caught me off guard and I said, 'no not the *girl's name* you know.' It was an awkward silence and we haven't spoken since.

Should I continue to have such distrust, the nagging voice in the back of my head, or how should I go about trying to ease my fears? I would never leave him, just the pain is always in my mind and it's wounds I can't get over.