Caught them in bed

So my husband has been really bullying me. Before Christmas i caught him in bed with another woman. I’ve also caught him buying drugs and i think he’s been drugging me. He’a got cameramen in the house filming with the media, and I really want out of the relationship but he won’t let me go. He says I am mentally unstable and says he’ll get full custody of the children. I am also being stalked. I don’t know where to turn to for help.