I have a morton's neuroma. After I have been off my feet for awhile, the ball of my foot hurts so I can hardly walk. Is that because of the neuroma?

Most likely. Morton's neuromas can cause severe forefoot pain, particularly after activity. Some say they feel like they are walking on a ball or that their socks feel bunched up.
It could be. This is a common cause of pain in the ball of the foot, but not the only one. See a podiatrist and be evaluated and x-rayed. Metatarsalgia, plantar plate issues, arthritis and other issues might be the issue. Plus, it sounds like you are in pain and am searching for relief!
Neuroma. Yes the neuroma generally hurts at the ball the foot even if you stay off of it. It is the compression of the nerve do to the surrounding tissues of the 3rd interspace. An injection with nsaids can help, in conjunction of orthotic wear. Finally the decompression surgery is the last option but might I add very successful in curing the condition.
Probably. A morton's neuroma is actually thickening and inflammation of the nerve that supplies feeling to the bottom of the toes. Once you irritate it by activity or tight shoes, it can be painful for quite a while. Sometimes, it requires a steroid injection. If this doesn't help, either sclerosing injections or surgery are indicated if pain is too severe.