I just need to vent 😭

I'm so upset and I shouldn't be.. but we tried for a baby for a few months back last September and we were one of the lucky ones who caught straight away. We found out we were pregnant on Christmas Day and Everything was perfect. New Year's Day we told our parents.. my MIL was not happy.. despite us having careers, a mortgage and we've been together 6 years with a 3 month break around 3 years ago.. we are engaged and I stuck by her son even when he got another girl pregnant on that break. We have him every Mondays, Tuesdays and Wednesdays. I arrange my work around him so I can be part of his life and I love him as if he were my own. But my mother in law seems to have a problem, a huge problem. She just cannot be happy for us! My partners sister is now 17.. she's on bail for GBH... and my MIL is constantly ringing asking for help because she's finding it hard to cope with her temper tantrums and childish behaviour. She got kicked out of school, she thinks it's cool that her boyfriend and her have the same court date 😳 she doesn't work.. doesn't have a penny to her name.. she just loves trouble. Going back about a year ago, she asked me to take her to the doctor so she could have the implant because she had just got into a relationship. I did. Fast forward to Valentine's Day this year.. we have our scan and I'm so excited. I work my dates out as 13 weeks and 2 days. The sonographer asks me when my last period was and starts searching around my belly. She can't get a clear enough picture and decides to do the transvaginal. And there he/she is. On the little screen, tiny, delicate and just perfect. However.. there was no heartbeat. The size of the baby did not match a 13 week scan. More around 9... so I was advised that I could wait a little or opt for abortion. I trusted my body and sure enough, 3 days later, I miscarried. We buried our tiny baby.. the size of my fingernail. We were destroyed. Not one person from his side even asked how I was.. the response I got from his MIL was 'yeah well I had three'. I was fuming. 3 months on and we have had no luck. However, we et a call and GUESS WHOS PREGNANT. His 17 year old sister.. and guess who's over the moon about it, already gone out buying and saying how excited she is.. yep.. my MIL.