Family at war :(

This is a long one but please bare with :( 
So my husbands family like to think they are very close. Yet once you look into it it's literally  falling apart. 
There are 3 brothers and 3 girlfriends/wives. I get on really well with the other girlfriend and the other one just wants to make war. 
Her and I have never seen eye to eye and recently she decided to drag herboyfriend  in to it and now the brothers are at war... And they are blaming me for it. I know I'm not the one causing trouble as the other girlfriend agreed with me and so does the other brother. 
We both knew we didn't get on and I've always tried to be civil but recently she has just gone crazy. I'm pregnant and I really don't know what to do. I can't stop crying. I've spoken to my mother in law and she said that she will sort it but this has happened before and I know it won't get sorted. 
I'm trying not to stress for my baby or for my husband but is so hard. 
I just am at a loss as what to do. 
Is there any adivce anyone has for me. I'm. A woman who is desperate. :( 
Edit.. My husband has totally backed me and knows exactly what has gone on between me and the other girl in the past. But him backing me is what's making it worse :(