How do I stop obsessively checking if my boyfriend is cheating?

My dad cheated on my mom for 13 years. I cannot stop obsessing over the fact that my boyfriend might be cheating on me even when I know he isn't. I have full access to his phone, social media, and e-mails. I never find anything, but I'm obsessed with constantly checking just in case. How do I stop this? It's driving a wedge between us.