Be honest about your feelings
Rather than fly into a jealous rage every few weeks (or days) and risk making him crazy, talk to him about your feelings. Let him know you want to trust him but you're having issues. He might be able to put your mind at ease if he knows you want to curb your jealous side.
Stay away from his stuff
Paranoia plus jealousy combined with scanning his texts and email messages for suspicious content is a recipe for disaster. If anything legitimately concerns you, bring it up with him right away rather than driving yourself nuts with going though his personal messages. Invading his privacy for no reason will only get you into trouble.
Ask yourself why you're so jealous. Have you been burned in the past? If so, don't let past problems ruin a perfectly good thing in the present. Tell your guy why you've got jealousy issues so he doesn't think he's the one who's done something wrong. Good communication should help curb the current problem.
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