Cleanliness Issues

I just moved in with my man but his mom raised him to think that only women clean and... his mom is a hoarder. We have her old house since she moved out. He is sentimental and has a hard time letting go of things. It makes me very anxious and even my prozac isn't even helping me calm down. How can I help him clean/organize the house? He wants to help but gets defeated because it is such a huge mess.