Hi My 2.1yrs Old Sun Is Suffering From Loose Motion

Hi
My 2.1yrs old sun is suffering from loose motion for than ten days. I gave him a suspension and qhenever it is used motions become thick like precipitates and when suspension is stopped again watery loose motion with bad smell five to six times a day. I hv also given him sachet mixed with milk but same condition persist. Can you suggest anything please. He dont hv temp but sometimes he do vomiting. Thankyou for your suggestions