If you have a cold, then this is a viral infection and it sounds like you also have a stomach virus with it.
You just need to get plenty of rest and drink plenty of fluids and there is no need to visit a doctor unless your condition become a lot worse or your symptoms continue for a long period. Normally it can take a week to two weeks to get over flu/stomach flu properly. Anything longer than that and you should possibly consider seeing a doctor, but other than that, there probably is no need. Viruses normally clear of their own accord if your immunity is good and at 19, I would think yours should be.
Take some extra Vitamin C to help raise your immunity to fight the infection.