There is no reason at all why you shouldnt massage yourself. I got interested in massage because I had health problems helped by massage. I went on a non professional course to learn massage and self massage and have been hooked since. It was an adult education course I did first, which cost abour £100, and gave me enough skills to massage myself, friends and family.
You can buy massage rollers with long handles to massage your back, but Ive not tried them.
There are lots of courses out there, and books that can give you the basics.