What’s the reason

Is there a actual reason why I feel good some days in my relationship n other days I feel like ending things for no reason. Idk why.??!! It’s been half a year n I love him really do but that just throws me off idk my mind starts thinking things. How can I stop this.??? Or some days when he’s at work I randomly think he’s cheating n then I’m like how if he’s at work n then oh maybe he’s lying n he’s actually cheating🤦🏻‍♀️ I just ruin my own days..

Update: He’s never cheated, my ex’s have and I think that’s where my issues come from....