Why isn’t my boyfriend’s SIL talking to me? Help!!

I’m going to try to keep this as short as I can. My boyfriend and I have been together for 3 years, he’s 22 and I’m 19. We’ve been through a LOT and I feel a lot of it is because we got together so young and we’re both trying to grow up. He also has bipolar and a few other mental health issues so that also makes an impact to our relationship.

His brother and SIL have been together for 5 years, they’re 24 and 27, and have a 3 year old that I love. Over time, I got really close to his SIL and we’ve been there for each other a lot. A few days ago, my boyfriend had an anxiety attack and contemplated ending our relationship because I told him I wanted a baby after our loss last year and his family gave him a hard time. (Not that they knew, some just like to bitch). I know it sounds crazy but in the moment, my emotions were high.

So I tried to call his SIL and ask what birth control she likes and uses. She didn’t answer so I just left a text, never read. My boyfriend ends up telling me that he talked to them prior and told them everything. He says they didn’t say much except to just do what made him happy. We just spent time with them 2 weeks ago and it all seemed okay. He also tells me that they had issues again. I know she’s told me before that he cheated on her three times and is now talking to one of them, a girl he works with. So she’s been mad at him for a while.

I just don’t understand why she won’t talk to me anymore. She’s talking to other family members and still hanging around them. And is all over social media😔