17yeards old. hard to gain weight. no beard/no body hair. had prevention surgery because i tended to have testicular torsion. do i have low testoster?

17: Not likely, at 17 your metabolism is quite high. A balanced diet and excersize is the way to go. If an exam is normal there is very little chance of having a low t once you have gone through puberty.

Puberty: Boys (and girls) go thru puberty w/specific stages as popularized by tanner (http://www.Fpnotebook.Com/endo/exam/mltnrstg.Htm). Development depends upon hormones like testosterone as well as genetics. Not every boy/man will have lots of facial or body hair. But all boys/men should have some pubic hair as early as 10yo & late as 15yo w/axillary hair by 14yo. So if none of that by 17yo, go see doc.