I have major trust issues that have prevented me from trusting

First of all, you shouldn't be looking for "evidence you're being used" you should be looking for tips on self love and acceptance because the problem is not with the actions of the girls in question but rather the fact that you personally feel so bad about yourself that you don't have faith someone could genuinely like you without an ulterior motive.
Forget about debunking a girl's "real reason" for talking to you and focus on building your own self confidence, learning to trust others and realize that by virtue of being human you are enough and worthy of love.