Trust issues...

[Professional.]

I still have this problem with some things in life.

[Caffeine]

I had some pretty severe trust issues when I was a teenager. Between girls and backstabbing friends, it's sometimes part of the experience of being a teen. Are you still in this age group?

As you meet good people and develop bonds with them, I feel your trust issues will begin to subside. This is what I experienced, anyway.

[WTC]

You should trust your parents always. If you don't trust anyone this may cause issues in the future. You need to learn to trust people

not necessarily true in some ways. Ok they are your parent/s.
But a parent may have diffrent views on things someone not of their "age"
& " experience would have. Remember they grew up in a different era.
-OP, trust is something a person has to gain, if you feel your GF is trusted then how about moving out with her?
Get your own place and move on...?