Dealing with jealousy, getting past it?

My boyfriend and I have been dating for about 3 months. We spend a lot of time together outside of work and time with our children (I have one, he has 2). I know I consume his free generally. I know there isn’t anything he is doing.

I have become jealous, uncomfortably so. I have never been jealous with other relationships. Never. Not even a little. I didn’t care what was on their phone, I didn’t get annoyed by porn habits. Want to read/watch porn on your phone, have close female friends, go out with said females? Cool. Didn’t care.

This relationship though doesn’t feel like that. I don’t understand the change - we are very open and honest with each other but sometimes it just eats at me.