On the Anxiety, Panic, and Phobias forum there are a number of folks who share this trait - finding it difficult to leave the house. I think the treatment is generally exposure, as with most social anxiety issues - you force yourself to face going out and gradually become acclimated to being outside, and then success breeds success. "Success breeds success" is a very powerful strategy - I used it for decluttering and yes, it does work. I hope that gradual exposure can eventually bring you to that point where you not only CAN leave the house, but also ENJOY being outside of the house.

For support from people who suffer from the same condition, the Anxiety forum would probably work better than this one (you can open an identical OP there - the site allows x-posting on two forums); you would get answers here, but you would get many more answers there, because over there, it is one of the main recurrent themes.

Also, group therapy for anxiety would be good to try.