Hi, It is important to know if you observe hygienic practices during masturbation or not. Using a sex toy and then making an oral contact with it can predispose to infection which can cause vomiting and diarrhea. This occurs after few hours following the infection. If you are hiving these symptoms every time you do masturbation and it occurs immediately after then it is more likely tho have a psychological cause. It is due to the overactive autonomic nervous system and sympathetic and parasympathetic nervous system. Masturbation is commonly associated with guilt and anxiety at your age, though no such physical associations are actually present. Most of the time it is in your thoughts. Doing masturbation once in 2 weeks is acceptable as normal. Please do not have any guilt or stress because of doing it. This is a normal behaviour shared by most people at your age.