Welcome to HCM.
on your right buttock at the age of seven year old is not having anything with your present problem.
Only spinal cord injury
will affect you sex. If it is so, you will not having total erections at all.
It seems that you don't have any problem at all. A man cannot continue his sexual activity as if wth his early twenties for ever. One can perform twice a day or more than that during his twenties and immediately after few years of sexual activity. This cannot remain for ever as to our wish. Male sexual instinct has its own refractory period. It will take considerable time to get aroused on stimulation varying between few hours to few days and even few weeks according to chronological age and sexual activity age. This will further worse after the age 50 due decline of hormone levels.
So as per your statement sex onetime a day is normal for you age. More than this frequency will end in erectile dysfunction
. You can do well with some drugs only for sometime. Then worst thing will follow a total erectile failure and not able to stimulated even by drugs.
So don't worry about your childhood injury
and content with what you have blessed with which is quite normal for your age.
Wish a great day.