I Am 63 Years Of Age And Worked 28 Years

I am 63 years of age and worked 28 years wearing steel-toed boots pounding the concrete floors in the name of keeping the share holders happy.I now experience pain in my feet and most of the major joints of the body.
Along with that I have some kind of gastrointestinal thing going on.I have lots of gas and can hear lots of rumbling of the got going on.
A friend told me I should try magnesium citrate
I also sometimes experience vibrations in my heart.
What should I do?