How to comfort your girlfriend when she's sad ?

Me and I girlfriend have been together for almost 5 years i been wanting to have kids with her but every time I talk to her about it it upsets her. She said it's not a good idea to have kids right now she's worried if we have one I'll leave her. It's happened to a lot of her friends also she's seen it on TV she doesn't want to be one of those girls who ends up having 2 or 3 kids with 3 or 4 different guys I tell her its not gonna be that way i think she's been watching too much of that Teen Mom show she likes. I dont even understand that show it doesn't make no sense to me it's a bad influence on young girls i don't like it but she makes me watch it. She said a few of her friends are pregnant right now and single but they're stupid teens who made a bad choice were adults that's not gonna happen she doesn't believe me. One of her closest friends is 19 and pregnant she was engaged now she's single sounds to me like she made a stupid mistake. Yes i did divorce my wife i had years ago but there was a reason for that i told her I'm not leaving her just because we have kids. I do have 2 boys from my marriage she's never met them she said she doesn't want to. She's on the IUD right now she'll be getting it removed sometime here in the summer she's worried about ending up pregnant. How can I help her feel better ?