Tax credit and child tax credit , how do i claim now? legally married but separated? should we still claim ?

-should we still claim as a couple? husband still pays bills , food and mortgage but lives with his mum. I am a full time mother. I don't get any other benefit. We still see each other in the week and weekends as we have a child. He only sleep in different places. I am confused. He thinks its ok to claim as a couple but I don't want to get in trouble