My son had his appendix removed laproscopicly on june 20th 2017 since his cooperation he has lost weight he has gone from 115 lbs to 98 lbs. normal?

I don't think so.: He should have gained back a good bit of his weight by now. If his appetite has decreased then there is a reason why. An occult infection or inflammation would be a consideration, although being so far out from his surgery would make this less likely. He should have further evaluation by his primary care physician to determine the cause.