Trust issues & moving past them?

My girlfriend got with me by cheating on her boyfriend (who she didn't tell me about when we first met & began seeing each other) & when she finally did, she told me she would leave him, but this turned into 6 months of will she / won't she (i probably should of walked away, but that was too hard based on the way i felt about her). It got to the point where I said if she didn't leave him, I would be gone.

She did & we are together now. But am struggling with trust & me feeling hurt & reacting to certain things is affecting the relationship which is really frustrating.

For example, it's been now 8 months together (just us) but last month she told me she was getting a parcel delivered to her mum's & she needed to go pick it up. The box for the parcel she brought round to my house & when putting it in the recycling I noticed it had her ex boyfriends address on it. So I asked her how her mum was when she picked up the parcel, she told me this story about getting parcel & her mum etc... so I brought up the fact it had her exs address on it. She then told me she lied because she didn't want me to get upset & it was a mistake.

Things like this have put me on edge & it's making me paranoid. Like when she gets WhatsApp messages. I wonder who it's from or I wonder where she actually is. When I bring things up she says she is struggling with me not trusting her. What can I do to stop feeling this way? Because me getting like this is pushing her away.

Trust issues & moving past them?
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