Family is hurtful just for the sake of being hurtful

My family (more specifically my mother) likes to say things about my weight and appearance. I am slightly overweight because of a thyroid issue and PCOS, but I am working hard and taking all the medication to work on it. 
My mom is also slightly overweight, but weighs about 5 lbs less than me at the moment. She likes to bring that up at every possible opportunity. For example, she bought me a jacket for my birthday recently. When I tried it on (and it got just fine) she said, "if you're too fat for it, I'll take it."
She has also said things like "Sure, I'm fat but at least I have the excuse of having carried children." 
She isn't the only one, either. All of my siblings say things too. My little sister told me today that she was afraid to get pregnant because she didn't want to end up gaining weight and getting stretch marks like me. 
I am a grown ass woman. I have medical issues. I buy my own damn clothes. I don't understand why they all care so much! 
I'm 5'5 and about 180-190lbs (it fluctuates a lot) and even my DOCTOR has told me hat I'm fairly healthy aside from a few hormonal things and PCOS. 
I'm posting anon because I'm honestly a little embarrassed.