Advice about mother in laws

Mindy • I am married to an amazing man, mommy to an incredibly gorgeous boy (10.31.2015). I am 27 years old and we are trying for baby #2.
I am posting for encouraging advice, not to be bashed. If you can not be nice please do not comment. 
My story/issue: I am a FTM, 28 weeks pregnant with a little boy☺️. I have all of these fears that have all of a sudden come rushing in, a sense of jealousy maybe (who knows). I like to tell myself I am not jealous. My mother in law is a bit on the crazy side and still has baby names for my 28 year old husband (her son) and it seems when she calls him these names, it's simply out of spite. Just to get at me. There are several more underlying issues with this woman that would just be too much to put into words. My issue started with how she practically flirts with her son and craves his attention especially when I am around. She talks about her sex life with him and how she has to have a hysterectomy and how bad the bleeding was and how her vagina hurts, etc.. Things in my opinion no mother should discuss with their kids let alone son. My baby shower she tried to completely take over. Just started placing decorations wherever I said I didn't want them and put ones up that I said I didn't want put up. She keeps picking stupid pet names that she says she wants my son to call her knowing that we have a family name that my husband has also agreed on for the grandparents. I am worried when he is born she will try and Weezel her way in and act as though she is his mother. I am afraid she will be around him when he takes his first steps or says his first words because I will be at work and she will rub it in my face. I do not want to feel the sense of competition I already feel from her with my husband especially not with MY OWN son. I don't know how to handle this. It may seem petty, but if I put the entire back story here we would be reading all night. She talks about how when the baby is here she can't wait to feel his skin on hers, kiss his face, hug him, sing to him, read to him and so much more (her words). I guess out of selfishness I would be happy if she wasn't able to be in the picture all of the time and she didn't live so close. I hate feeling this way! Help.