17 Months Old Child Started With Vomiting And Diarrhoea. Should I Consult A Doctor?

Question : My son, who is 17months old. and used to never get sick, got sick while at daycare on Tuesday Oct 30th. he was sent home because of vomiting and diarrhea. He threw up and had diarrhea the rest of that day, wed and thursday. On Wed I took him to the dr and the dr barely looked at him and said he had a stomach virus, if he kept vomiting after 2 days to take him to the ER. Well Friday he had nothing, not even a bowl movement. Saturday morning, when we pulled him from his bed, he had vomit all over his bed. I called the Advise line, and they told me to just observe him and only take him in if he isnt keeping down fluids either. Well he is fine during the day, but for the second night in a row, he has thrown up at some point in the middle of the night. We got him out of bed today and he had thrown up. he doesnt wake up when he does it, or at least there is no sound. Should I just take him to the ER? He doesnt even act like himself anymore, he used to be very indepentant, and happy. He'd run around playing. now he is clingy and has to have me holding him no matter what... what could it be and what do i do??