Last Straw: SIL announced pregnancy and doesn't realize how much it hurt.

So I have two SILs. One with three kids, one without. Both married about five years now, to DHs brothers. We were already dealing with infertility when they got married, so I started to panic, realizing either could get pregnant before me. Well, SIL #1 did, practically on her honeymoon. Has three now, and each announcement kills me. The last two, they've used their first to announce it to family. So when we were all gathered in my living room and he was asked to "share his secret", I instantly knew what that meant. Thought I thought it was #1, it was really #2's announcement. This hurt worse than Fertile Myrtle. They've joked about not wanting to get pregnant, or accidentally wanting to get pregnant, etc. It hurts every time but I don't say anything because why should they not talk about something that's obviously important to them just because I'm there? I've literally had nightmares about them announcing, because I knew it would be hard. Thankfully we got pregnant six years into our marriage and we now have a toddler, but we rely on embryo donation to have children, so I still grieve not having a genetic child with my husband. When we were given our son as an embryo, he was one of four. We transferred two and he was the one who made it. We transferred the last two in June to give him a sibling and miscarried. We announced to family before that, though. Guess where? In my living room, with everybody around just like this last Friday. So it was already painful just being together because of the deja vu. But then they announced it in my house where I couldn't escape. I couldn't feel. I hid in the kitchen and it was obvious I couldn't face them. Yet that didn't stop my BIL from writing their girl name on our patio wall along with the rest of the cousin's names. I understand the excitement over names but (a) they don't know the gender and (b) that's my freaking wall that I see from my kitchen and living room. Like, way to put it in my face and not let me forget. I hosed it all down as soon as they were gone. But how do they not know better? I don't know how to move forward. I wrote a very bitter letter to SIL, nearly a full page. Haven't sent it of course, because it's too rough. But I need to express my hurt. I don't know how to move forward, and I certainly don't want to see SIL as her bump grows. I've been wanting to cut them off for a long time because they've never reallly been respectful towards me, the whole family. But I don't want to do that to my husband, and they won't take me seriously anyway. They'd just say I'm overreacting. 
Ugh, what a disjointed rant. But seriously, I can't keep my thoughts straight right now. Even hubs is unsupportive. I feel so alone and angry.  

ETA: Sorry, I was writing in stream-of-consciousness. We have a cinderblock retaining wall around two edges of our back patio, which is concrete. We live on a hill so it keeps that one section flat. I gave LO and the cousins the chalk so they'd stay put. It's a dedicated art wall since the Washington rain takes care of it. But this day I was not willing to wait for the rain to deal with it.