Do tu trust your sixth sense ? Your gut?

Well tonight my bf is working a different site ( he does security ) and he met a girl who is married and from what he said they talked for a while before she had to go, and they even became friends on fb, so we’re on the phone and he goes quiet for a little and says that she messaged him... idk why but I got a bad feeling about it... like i don’t trust people at all... she messaging him to ask if he was working there tomorrow... ?

I don’t know what to think I mean I was ok with it until I learned that they added each other on fb which tbh I didn’t like but at the same time was like not a big deal until she messaged him and they just had been talking at work? Sorry I’m really confused or am I making a big deal out of this?

What do I do ?