i am afraid i can't tell you how you can overcome this situation, as i am also going through something similar.
however, since you mentioned that you want to give it a shot, i would suggest that you start talking to your partner about all the thoughts you have in your mind. tell him why you find it difficult to trust him anymore. talk to him about what you think can help build it back. if required, you can also go for professional counseling.
whatever you do, make sure that you are giving it your 100 percent, as else the cracks in the relationship never fill up.
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