Husbands brothers don't like me

Let me start out by saying there's no horrible reason why they don't like me. My husband and I have been together for 10 years. At the beginning of our relationship I got along well with his brothers. We got married and had two kids in the last five years. His brothers don't like me because I'm a SAHM due to the fact that my oldest has autism and requires hours of therapy a day that takes place in home. They feel like I should have returned to work 6 weeks after I had my son. It made more sense finacially for me to stay home and look after our children because of my son's additional needs. My husband makes great money at his job and we live very comfortably. This past year his brothers have further ostracized me and made it known they don't like me. They also talk down to my husband and make him the constant butt of mean jokes but that's a different story I suppose. Brother number 1 let's call him Steven, planned a surprise party for brother number two, let's call him James. Steven invited the whole family including spouses except me. He then had the audacity to ask me a HUGE favor just a week after the fact. Before I had kids I had a successful baking business and my cupcakes were my best seller. Steven asks me after brazenly not inviting me to James' party if I would bake 500 cupcakes for FREE for his upcoming wedding because his wife to be wants cupcakes instead of a wedding cake🙄 He didn't even have the decency to call and ask he sent me a TEXT MESSAGE. I didn't even reply because I was so upset with the lack of respect. Fast forward to today. It's my husbands grandfathers birthday. He lives two hours away. James called my husband this morning and asked if he wanted to ride share with him knowing full well that my husband would be taking me and our children down there too. My husband said he couldn't because he was taking the family and James replies "that's too bad". Like what the actual fuck?! So on top of this, I'm currently 13 weeks pregnant with my third child (high risk pregnancy) and have HG. I've been so sick I've lost 30lbs since week 7 of pregnancy. I was planning to try and power through to make to his grandfathers birthday but it's so obvious I will just feel uncomfortable the whole time so I have chosen not to go. Maybe if I felt like myself I would feel stronger about standing my ground but I just feel so defeated. My husband has elected to go which I understand because it's his grandpa I just don't know if I'm letting his brothers win by hanging back and not going just like they want? Any advice would be appreciated. I feel so lost right now.

EDIT: it was a Facebook invite. My husband showed me when he received it, you can see everyone who is invited. All other wives were invited.