Helpless

So my boyfriend is 34 and I'm 21. He has an 11 year old son.  The mother is legitimately crazy but he still feels he needs to kiss her ass because of the kid. It's such a helpless situation because she's not going anywhere. She will be in his life forever because of the kid. And ahe always texts him dirty things trying to get him to come over and have sex with her. And she's almost 50 years old too. And she knows about me. She calls him nonstop especially when we are going together and when he answers and I hear hen talking and him kissing her ass and calling her nick names like he calls me it kills me. We have been together almost two years and she war never an issue because his son was never in the picture until about two months ago. So I'm still getting used to it. But honestly I don't think I'll feel comfortable with it until the day we have our own kid. Until then I will always feel that she has an advantage over me because she's the mother of his child. I love him a lot but I'm 21 years old a good looking girl in shape who has a bright future ahead. I don't want to be in competion with a 40-something year old. I just don't know how to let go of my jealousy and anger towards this situation. It absolutely kills me and it's hurting our relationship. Any advice would be freely appreciated!!