Need to let it out

I had my first pregnancy end in miscarriage this August. This month after ttc and waiting for a period that never came, I was diagnosed with pcos. I've been trying to cope with everything and not be consumed by the grief. I also wanted to maintain some privacy. For that reason I chose not to tell my family or my inlaws. The only people I told were my best friends and my husband's sister (he knew all long). I told his sister because she had just given birth in September and she went through a miscarriage herself. I needed her to understand that I was keeping my distance for personal reasons not because I didn't love them or feel joy for her. She said she understood. Since then his parents have greeted me with their phones showing their granddaughter in my face. They never stop talking about her. Not even when I get quiet. This is their first grand child so I understand their excitement. Still I can't help but dread being around them. I decided to tell his mother tonight that I was sensitive to the topic and open up about my diagnosis but not the miscarriage. I never got the chance. Before I knew it, his sister with new baby in tow came in and his mother said "oh yeah I invited Amanda. Hope you don't mind". Oh yeah, like she forgot to mention it all week, or the entire time we were at lunch earlier that day, or while I was busy cooking dinner for two. His sister didn't bother to warn me either or make sure I was OK with it. They just ambushed me. I had to get air and walked into the back yard trying to stop myself from crying. My husband came out and told me he would have my purse and keys in the car so I could leave and go home and he would take care of everyone else. So I drove home feeling guilty for leaving him to deal with the mess I left including the food on the stove. I don't know how to feel knowing they probably will know after tonight. His mother is the type of person who says well intended yet nonetheless hurtful things. It makes me want to avoid them. At the same time I feel guilty for having my husband in the middle. How do I cope? This pain just seems to get bigger rather than subside.