So let's see, Kehliouise, your mother grew up in a family where birth and pregnancy conversation was taboo and raised you to believe pregnancy was dirty. When you announced your first pregnancy your mother judged you and condemned you. When you announced your second pregnancy, rather than supporting you and celebrating with you, you're mother basically asked if your child was a mistake. I don't think you should be asking "why the anxiety?" so much as "Why should I ever feel safe sharing news of something as precious and joyous as a coming baby with people who are so hard-hearted they see it as a curse rather than a blessing?"
Don't feel alone. Well you and your DH might be alone IRL but I'm in your "virtual world" boat with decided non-support. This is my eighth pregnancy and seventh child and I didn't want to tell either set of grandparents. They all have thought we had too many children when I was pregnant with my fourth. My mother lives about a 50 minute drive from here and didn't visit until my fifth was a few months old when her friends kept asking about the baby.
With my build I can hide a pregnancy pretty well and didn't have any urge to tell grandparents. From a BIL we got the comment, "Well, congratulations if that's what you guys want" and from an co-worker DH got "You guys are gluttons for punishment, aren't you?" At four months DH said we *had* to tell GPs as keeping the secret longer would cause more hurt feelings. We compromised and I called his mother and he called mine. My mother is far more conscious of boundaries with DH than me. I think DH considered his talking to my mother to be part of his duty to protect his pregnant wife. (So sad that helping my avoid speaking to my mother is reasonably considered protecting me.) We got the deed done and now I'm going to a DH's family event this weekend. I'll dress so that they'll have no idea I'll be 21 weeks.
Anyway, I guess all I really have to say is, "You're right, they're wrong, it sucks, and you're not alone." It's not great but that's the only truth I have to share with you on the topic. I hope you can get some encouragement from it.
P.S. Since you have no IRL support in this pregnancy (outside your DH), maybe you can try connecting with folks who consider children a blessing like LLL, CCL, some homeschool groups, and such.