Am I wrong to be pissed off

Okay so me and my boyfriend/baby daddy bought a camera not to long ago. Anyways on Friday he went out with his friend to go smoke and I am Okey with it some guy time and took his camera, he came back and ask for the keys to the car cause his friends car was heating up so I gave them to him to help a friend. On Sunday we go to the pumpkin patch take pictures of our son and when we get back home I asked to see the camera he didn't let me touch it got all defensive. So I know something was up. I kept asking him what are you hiding tell me the truth it's another girl pictures in there huh and he wouldnt tell me. So he went to work the next day and mother fucker to the memory card out so I wouldn't see the pictures. So when he went to the bathroom I looked for the memory card and found that he took pictures of another girl with our camera. I blew up on him and he is telling me I am over reacting cuz there just pictures. But i told him then why where you hiding from me.if it wasn't anything you just make me think wrong.