TEEN REPORTER KAMILLE BOSTICK SAYS: What happened to make you think that he can't be honest or true? What has he done that makes you not believe he'll act right when you're apart?
Ask yourself some tough questions about why you feel the way you feel, and then work out whatever issues you have. If your boyfriend is a good guy then he deserves a chance to have you not think everything he's doing is about deceiving or hurting you.
If he has been dishonest or untrustworthy, you might need to decide that things are broken between you and it would be better to end the relationship. It's a hard choice, but it might be one you need to make.
If you're the problem in all of this, and want to do better at trusting your guy, you simply have to start actively trusting him more.
Take things on a case-by-case basis.
The next time he says he wants to go to the mall alone, let him, and while he's gone, don't let yourself think he's up to doing anything that isn't right. The more you do this, the better you'll get at trusting him.
If you can't believe he'll act right after you're out of sight (or he is), then you're setting yourself up for some serious stalker tendencies (how else will you keep track of him?). I doubt it will go that far, but it will be nearly impossible to keep a track of him, so you'll only drive yourself crazy by trying to do the impossible.
Trusting someone doesn't mean being blind to facts or reason but it does mean being able to close your eyes or turn your head and not think the worst. Good luck.