Abusing husband please give me advice

We have been very happy the whole time he was always extremely supporting and loving and respectful but ever since his mom and 2 months later his dad died and just 2 weeks later we lost our 9 month old daughter where the doctors werent able to tell us why he went crazy. The loss of our babygirl destroyed our family. We have a 4 year old son and he doesnt even know what happened. My husband didnt look at me and didnt talk to me for days when she passed away. He started taking drugs and right now I dont even know what he's taking. It started with him coming home drunk and high and slapping me but he was gone once he was sober to go out again and drink and take drugs. He's with this girl now called Devon. 

They're dating she's staying at our place a lot , she knows about me and my husbands besr friend lives with us as well now and his old friends who are my old friends now try to help me but my husband wants me to tell them that Imm okay with that and just dont talk to them anymore. So I dont and his best friend is moving out in a few days as well. They dont know he's abusing me and even used me for sex when I didnt want to. I'm too scared to tell them but to be honest I dont even want to. I love him so much I dont want to give up on him now we have a son we have been through so much and I know he's still in there he just needs to stop taking drugs but he doesnt let me even tell him that. I'm so done I dont know what to do.

I love him so much and he loves me too everyone always told me that and he never hurt our son or let him see how he hurt me. 

I'd leave him the second he hurts my child or even yells at him but honestly he hugs him and holds him and thats when he's calm. I'm just trying to take care of him and especially my family. I would forgive him for the scars he left on me and all those marks and forcing to have sex with him but it just hurts so much that he's treating her all good but not me.