How to get over jealousy of my boyfriends ex?

I sometimes feel crazy when it comes to this situation. I don't want to be jealous of his ex, but the fact of the matter is I am. I ask myself why. I have come to these conclusions . #1. He has a child with her. I will never be able to have a child with him. #2 He has to stay in contact with her because he has a child with her. I understand this. But the contact they have I think is somewhat inappropriate. She makes him feel like if he isn't treating her the way she wants to be treated, he will not see his kid. She calls several times a day and is disrespectful to me if I answer the phone. Telling me I have no right to have his phone because she needs to get ahold of him because of his daughter. He tells me to just ignore her. He does everything he can even if it is being more nice to her, just to avoid conflict. #3. She wants him back bad! She sends him text messages asking if he wants to move in with her, or calls and says she wants to work things out. She just does not let go and move on. #4. He goes inside there home when he goes to get his daughter and brings her home. This last time he stayed for a half hr inside. He said he was in her room and getting her school pictures. I just do not see why he has to even step foot behind closed doors with that woman. Just knowing she wants him back makes me feel ill that he would allow her to get that close to him. He insures me he does not want her back. But I sometimes feel I am a rebound, a get back at her girl. I have been in some really crappy relationships in the past. And don't want to be hurt again. Otherwise he is a good guy, treats me well. Anyone have any advise? I just don't know what to do or how to get over this.How to get over jealousy of my boyfriends ex?
If it bothers you that much you should find a guy without kids. No sense in putting yourself through something you're not emotionally ready to deal with. Besides, it sounds like he's still sleeping with his ex while he's with you and that's never ok.