One of the first thing I noticed in the question is the use of the plural use of girlfriend. So, this may mean that you have more than one girlfriend which would make you the person cheating. Next, you need to sit down and talk to your girlfriend. Are you trying to control her?Do you require her to "check in" with you ? If you are being controlling and need to stop.
There is no test to take that will tell you if your girlfriend is cheating on you are not. Girls all act differently and the fact is she is either cheating or not and no test can 100% tell you.
if they are really silent when there by or talks to him alot or flirts with them
The biggest lie most guys tell is they aren't cheating on their girlfriends/wifes when they really could be.
Not likely. He seems to be cheating on girlfriends with other girlfriends.
have sex with him
If you have to do it in secret, yes.
Well he obviosly is if he has girlfriends
No, But if you have a feeling she is cheating on you then you are probably right
Yeah i would say so if ur dating your "girlfriends" best friend that's not good.
Yes it is cheating and they cheat because they might be confused or think they are all that with two girlfriends.
you look at them with a neon darklight, stains appear
There are many songs about girlfriends catching cheating boyfriends, including: "Before He Cheats" by Carrie Underwood