What is the best way to get my husband to go to the doctor, especially if he has to pay?

Tough problem: Men consider it "manly" to put up with discomfort and illness. A visit to the doc implies some loss of that manliness. You should find out about his condition (use the internet) and discuss with him the consequences of having it taken care of versus the possibility of chronic problems and disability. The cost is a difficult one but many docs will negotiate if you offer cash.