Jealous of my husband's past!

I don't even know if jealous is the right word. I've been married almost 2 years to a great guy, hardworking, trustworthy. We are in our fourties. I have a 15 year old from a brief crappy marriage. I left after 2 years, he died a year later. My husband has 3 kids, 18-26. He was married at 20. Worked endless hours to support the wife & kids. Seemed like they had a pretty humdrum relationship, no passion or anything. It was so so for about 12 years then for the last 10 she stopped participating with the kids & family life. He worked nonstop & tried to take care of the house & kids at the same time. After 22 years he finally got fed up & left. His ex lives across the country ( took the youngest with her) the others live their own lives. He was never really close to them physically or emotionally, I think a lot due to his crappy upbringing. The daughters I've only meet once so they are not part of our daily lives at all. He texts, emails & calls them.
So what is my problem? I wish he didn't have kids. They just remind me that he was with someone else. He doesn't communicate with his ex at all. I know he has zero feelings for her. I feel like I'm angry at his younger self for marrying her in the first place (he was 20!), angry that he kept making kids with her. The thought if him getting her pregnant & giving birth to these kids makes me want to cry & vomit at the same time. When their birthdays come around it's just another reminder. Through my day when there is reference to the year he got married or the time when she was pregnantbor gave birth it reminds me. You'd be surprised how many times you hear 1989 in a day! I'm angry that he worked his butt off for someone who didn't appreciate or take care of him.
I try to concentrate on the here and now and the facts: He loves & is married to ME. I make him happy & do sweet things for him like she never did. He says he never had a sex life before and never really liked sex. We have a great sex life & satisfy each other. He is a great provider, never mean or nasty. He doesn't smoke, drink, gamble etc.. I know he wouldn't cheat in a million years. Emotionally he's a little awkward but he's trying. Damn that "mother" of his!
Do I sound like a lunatic? Will I ever get past this? I had a very different past. Had a two year high school thing, a long relationship in my 20's, a few boyfriend's before and after and awful promiscuity in the younger years. He would be disgusted if he knew half of it. He had very little experience, got married, had one disastrous girlfriend and met me. I've always been a bit jealous & possessive. How do I break free of these repetitive thoughts and feelings. He should be able to talk about his kids & I should be able to get over the past. The funny thing is I don't dwell on my past at all, just his!! Just jealous he shares kids with someone else, shared a home, a life with someone else.... Even if it wasn't very good! I hate to hear about women getting/being pregnant, giving birth, babies, people getting married young etc.. It drives me nuts because of course there are reminders of these things everywhere.
Even if no one reads this it feels good to get it out. There's really no one to talk to about this.