Does anyone else get mad at SO for no real reason...?

I keep finding myself getting mad or upset with my SO over small things or no reason at all. And before I know it nice made into a scene and we argue. I feel hormonal sometimes and almost like I'm searching for trouble. And I don't know why.... Maybe this is just a vicious girl thing we do to ourselves. For example it's just nature for men to be attracted to women who don't look realistic. And I found my SO following attractive nude women on instagram and it hurt my feelings and I brought it up. It turned into more than it should have and I was upset. I know it's probably stupid but I'm very insecure especially after having a baby two weeks ago. But my point is, I don't want to be like this. I don't want to sabotage my relationship over something like this. Am I the only who struggles with this? Any advice or feedback is appreciated....