Also. If you are lucky enough to live in an area that has lots of baby groups/activities, utilise it as much as possible. The support network that you can create through meeting other mums will really help. It will also help to fill up your time so that MIL doesn't have so much opportunity in being the only person to be involved in your life. I hope that you can sort it all out and start enjoying your time with your baby x
I feel your frustration as I had something very similar when I had my daughter, only it wasn't his mother. It was his "sweet" old nan! The woman was infuriating, and my partner just couldn't see how controlling she was towards me and my "spare time" (maternity leave)! My daughter was a very difficult baby who suffered from intense colic and would never sleep for more than 45 minutes at a time during the night, and flatly refused to nap at all during the daytime! "Sweet" old nan saw an opportunity in my weakness and fully abused it, partner couldn't see it, sleep deprived me was helpless, and all of a sudden in arrived PND! As horrendous as it was, the diagnosis alone was enough to open my partners eyes to "Sweet" old nan actually being a witch, so things started to change. Now, I'm not for a minute suggesting that you allow PND to set in so that you can get your MIL to back off! I am merely highlighting that it won't help it becoming a problem if you don't have that hard-hitting chat with your partner.