Trust issue help

So here's the deal I've never really had any trust issues until two of my exes left me for one of my friends or were talking to someone while I was dating them now that I'm dating this guy really care about my trust issues are getting the best of me and he might leave me and I want to get better so is there any advice anyone could give me so I don't lose him this guy makes me so happy but my trust issues get the best of me and i know i can trust him hes never done anything to hurt me and i met his parents and they love me and both our families get along i just dont want to throw away a perfectly good relationship over bullshit because of my exes i mean he lets me go on his phone we have our instagrams connected and he gave me his facebook password and everything he dlesnt hide things from me i just want to learn to trust him before its too late