Cheating fears

So I’m sitting on my couch right now, baby is asleep, and SO just went to the gym. He told me that he’s planning on being there for awhile.

It’s okay. Honestly. He’s usually at the gym for over an hour. It’s totally normal.

I KNOW he’s not out cheating. He always leaves his phone around me. Always invites me to go with. Nothing should set me off.

But. I. Am. SHAKING.

I can’t FOR THE LIFE OF ME knock the feeling that he’s lying and cheating. I’ve never even been cheated on. Idk where all this anxiety is deriving from.

I have GAD. I recently got switched to Lexapro after being off medication while breast feeding. Maybe that’s causing it. But i need help with some coping mechanisms or just like funny pictures or something to get my mind off of this.