Dear patient. Greetings from health care magic!!! I am Dr Thakker and shall be answering your question. I very well understand your anxiety about your weight and the digestive system. I will try my best to guide you through this. I would like to know the name of the powder you have consumed for weight gain. Most weight gainers contain high amount of carbs and stopping it suddenly should not lead to vomiting. However if it does contain steroid then your endogenous steroid production stops since you have consumed it for 3 monthns. Now if you stop suddenly your body will go into a crisis because your body has stopped its endogenous steroid production. The result is vomiting, mood changes, hyperkalemia and so on. I would suggest that you can do a 8 am cortisol levels in your blood from a reliable lab. if this is low, it means you will need exogenous steroids which can then be tapered to 0. Also you can send the left over from that powder for a toxicologic analysis to make sure if it contains steroid. I hope this helps you out. If you have any more questions, please do not hesitate to write back to me. Yours sincerely, Dr Thakker.