A very young man like you should not be having those physical problems. If you do not get them diagnosed now and get a handle on them you will have much worse in the future.
Many back problems can be kept in check (if not close to cured) by the proper exercise. Twenty years ago I was having bouts of severe pain down my right buttocks and leg. It was so bad that when the pain hit I had to immediately sit down. At the time I owned a feed and seed store and was in the habit of carrying 50 pound sacks of feed and hay bales on my shoulder. I was in pretty decent condition.
I had the problem diagnosed. It was discs L5 and S1 becoming too friendly with each other. The doctor sent me to a physical therapist who put me on an exercise program. To this day I continue those exercises and keep the problem in control. Another less severe back problem I have is being kept in control with ice packs and exercise.Obviously not all problems can be controlled with exercise, but most can be moderated.
As already stated, the pain in the wrist could be any number of things. You are a little young for arthritis but it could be. There are some natural "remedies" that help with some arthritis, but usually these do not offer a cure. I have found that Glucosamine Chondroitin
/MSM can be a help. For some reason in my case they seem to help the joints on the left side of my body more than the right side.
I guess that after all of that rambling my message is that you need to get a diagnosis. Then depending upon the results you can make a decision as to how to proceed. I understand that currently finances are limited, but delay could cause many, many future problems. You may also find that treatment could be relatively inexpensive.
My best wishes to you and your family.