Dealing with boyfriends paranoia?

I'm 24 & my partners 29. Wev just had our second child.. He's 6 weeks old now. My boyfriend used to smoke weed till about 8 months ago. We trust eachother when it comes to the opposite sex, but the problem lies when it comes to normal day to day stuff. He thinks I do nothing but play games.. He thinks I talk to people at his work and try make him look bad.. When I don't know anyone who works with him! I bought him a watch for fathers day.. It wasn't too expensive, around �100, he dozent like it.. Which is fair enough, but he says I bought him one he didnt like on purpose.. If I don't wear my slippers around the house, it's too wind him up? I'm a mother of 2 kids, I'm still tryin to get myself in a new routine with the new baby, I dont get much sleep... & feel like he's watching for every mistake I make. When it's good it's great, otherwise he's making me question my own sanity! Its putting a lot of pressure on the relationship, I don't know how to handle his extreme paranoia!! Please help!!