you not wrong, but not right either, females are much more emotional than men, there is no right or wrong with them, there is always a Grey area that they see that we don't.
she has trust and insecurity issues, you either gave her reason not to trust you, or one of her old boyfriends in past relationship did and you paying the price for his mistakes. You need to speak to her about it before one day it boils over and you break up over the issue. Honesty is not always the best solution, but in this case it is.
If you don't want to confront her, One thing you can do is to try and show more affection, show her that she need not be insecure and that she is the only girl you are interested in. Often if you apply this correctly she will feel better about her self, gain more confidence and the stop checking your phone

( the trick here is to make a point of showing interest n her alone, make her feel special as often as possible, a candlelight dinner here, flowers there, little "i miss you" messages during the day or even leave them on the pillow, suggest a weekend away just for the 2 of you etc. try and be romantic and spontaneous in whatever way possible. it will do wonders for your relationship.
I guarantee it will solve the problem right there and who knows, after a few of those weekends away it will probably solve alot of other problems too.
( how is that for variety post ?

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