What’s wrong with me.

Today my boyfriend and i went shopping. We come back to the car and after loading the car i sit in the passengers seat, i look over and my boyfriend has a note in his hand. He gives it to me and it says “Hey cutie” with their name and number. I got so mad and ripped it up. I’m glad he did show me and not hid it, but sometimes i feel like he plans out certain things to get me jealous. For example, the whole car ride home I kept thinking he had wrote that note himself and planned it all out. I don’t know it’s been bothering me and whenever he tells me stories or girls hitting on him it makes me mad and not want to talk to him. Also, i used to tell him the stories of guys hitting on me out of pettiness, but now I’ve stopped because he also gets an attitude when i tell him. Also want to add, we live together so when something like this happens i avoid talking and being in the same room with him. I don’t know how to overcome this, please help