The good thing about telling people early, is that if something does go wrong then you will have a lot of support. I totally understand the fear of something going wrong especially in early pregnancy. Have faith in your body and remember this is what our bodies are designed to do. But your MIL definitely shouldn’t have told anyone, it wasn’t her place to do so.
That’s wild for your in laws to share the news. I’m so sorry that happened. That action definitely warrants a conversation with them and they owe you an apology.