Pregnant & I feel so alone

This is my first pregnancy...I thought and what I wanted was a positive experience. But My significant others parents are making it very difficult for me. His parents are divorced. The father is an alcoholic and his mother is rude. His parents relationship has caused so much stress because his father can’t get along with his moms husband and he becomes so angry when he’s drunk especially when he starts talking about her new husband. (Keep in mind they’ve been divorced for 10 years already).And his mom says some really rude stuff to me like as soon as we gave her the news of my pregnancy she says “Yayy! Just too anymore weight!”... she also decided to make her own baby registry without letting me know, and continued to comment about my weight.. Ive talked to my significant other about how I feel and he says I’m exaggerating and am taking this the wrong way. The one person I thought I’d receive support from isn’t understanding me.. All this is not good for our baby, I feel so bad because he’s not even born yet and I already feel like I’m failing as a mother by stressing. My baby deserves a happy mom.. I could go into more details with his family and their issues but I’m just so tired of it all. I feel so drained.. I don’t know what to do anymore....