Hello, I have namechanged from my usual more silly name as I fear this may get a bit recognisable.
I'm at the end of my tether with the issues in my relationship (2 young DC) and the way I feel my MIL compounds them.
I guess this is a sort of cry for help. I have been leaning on a very good friend from work, but I cannot just keep burdening her. Looking for opinions on what I can do as she is remaining pretty sympathetic but impartial. Although she is "my" friend she has met P a few times so obviously doesn't want to say anything really bad against him.
Basically my P is (mostly) a good man and 95% of the time reliable and does help with housework etc. We have some problems where he thinks I'm too confrontational and our sex life is strained as I have body-issues not related to him but they make me really shy and almost scared of sex. He drinks a couple of cans of lager a few times a week after DC in bed which I have no problem with (I drink on weekends) , but if he goes out with mates he sometimes doesn't know when to stop and ignores responsibilities the next day which is a huge problem for me. Maybe happens once every 2 months, but still not good enough.
Last night he was going to watch something on his mates Sky after he finished work at 11pm and stay the night there as he was taking the car. MIL had DCs overnight. He was to sober up by morning and collect DC's at teatime. However he phoned his mum in morning to ask her to bring them down on train (she doesn't drive, and he has our car) as he was still drinking (at 8am!!!!). She just does it like a total doormat
. It is the same with everything. He just relies on her to pick up the pieces with his own responsibilities and she just lies down and takes it. It drives me insane. He drives me insane.
But every time we set down boundaries as a family of 4 she will undermine me.
For example, P works long hours with the firm paperwork etc and I also work. We were never seeing each other because of his long hours and I felt like he was missing his DC growing up. So eventually after much heated discussions we agreed he would take at least 1 day off a week to be with us. When we were visiting his mother, she asked why he wasn't doing any overtime and he told her what we had agreed. She said "Nonsense! Men who work never see their families - that's life" Then she turned to me and said "Do you want him to be a house-husband or something? I'll bet your dad was working when you were young, don't talk nonsense!"
I was

She makes comments about how she things childminders are unsafe for children and wrong IN FRONT OF MY DD WHO ATTENDS AN AFTERSCHOOL CM!!! 
She looks after the youngest when me+P are working then if I don;t like a descion she has made unilaterally (with or without P) she tells me that I should be a SAHM then if I want to have have all the say in my child's life! 
She calls me when she can't get P on the phone and she is hysterical if my phone is off for a couple of hours. Saying things like "I just want to speak to my son" . When I ask "are you ok?" or "what is the problem?" she will say something like "It's a private and personal matter between me and my son" - Well why the f are you phoning me then?!
She seems to think I'm some money-grabbing bitch who is trying to use her son when actually he is the one who is not taking his responsibilities seriously at times!
I bit my tongue for so long as she looks after the DC a lot and seems to adore them. But recently I can't take any more. Today I told her she is enabling him by taking on his responsibilities for him and that it's not good for anyone, least of all him. All I got back were replies from him and her that I was to apologise for "abusing" her!
She was meant to be bringing my DC back at 6pm. Waited til 7.15 then phoned her. She then announced she is just going to put them to bed there as she is worried about P as he called from callbox to say he "fell asleep on bus and his phone got stolen" (what a load of utter bollocks i replied and asked why nobody had bothered to contact me after my work finished at 5.30), then got the reply "Stop calling my son a liar, listen you to me lady don't contact me again bad mouthing my son" and now she won't tell me where he is.
This doesn't happen often with P but this is really making me lose respect for him totally and I think I want us to split because of it. Although he won't ever talk about it because his mother reassures him that "you don't need to answer to anyone son" 
It happens with her all the time though. She said to me last week that all I care about is money and children should come first! 
I try to be strong but I'm just getting swamped by it all. The whole situation is making me physically ill. Sweats, shakes, feeling dizzy/faint, sick a lot etc. If I stand up to him, we can usually work through issues if I make it clear I won't tolerate such-and-such and he will change it (ie-the no days off thing) but if I stand up to her I just get dogs abuse from both of them telling me to stop "bullying" her.
I'm so confused and just don't know what to do. I feel almost like I'm not allowed a say in my own children's lives sometimes.
Sorry about extreme length of post. Helped to get it all out !