mother in law being a bitch?

Mamatoruben • 💙💗💛💚
Ok so basically my fiancé caught his sisters talking shit about me for no reason at all... and he confronted them.. about it and now.. his mother is saying it's my fault that he argues with his sisters. It's all my fault since I have been with him.. he's turned horrible.
But before I met him he was on drugs out every weekend getting in trouble.
I do everything for that family, take the kids everywhere and always help.
We are moving into our first house together in December and my dad offered to buy me table and chairs... and he caught his sister and mother talking about me again... 
"Have you seen "princesses" new table and chairs .. and his mother said ... daddy's bank probably.
I ask for nothing it's what they offer to get for me to help. I'm not going to say no and be ungrateful. 
They put me down so much. And it's making us argue. 
I had a miscarriage this year in Feb. And 2 days later his mam and sister was drinking and came in loud and he asked them to be quiet as I'm sleeping I've been crying all night.
And his mother said "aw ffs get over it" and his sister said "so my kids are sleeping to"
He has 3 sisters and only one like me.
They are so horrible for no reason I keep myself to myself. 
Am I being sensitive?