Had the stomach flu" for 4 days (vomiting /diarehea are gone) but still feel so incredibly weak & just not right - how long does this typically last?

Depends. Everyone is different, and react to illnessess differently too. The norovirus is more virulent, and may cause you to be feeling week for 3-7 days. If you are generally healthy, keep your fluids and electrolytes up, slowly get back to a normal diet, and you should start feeling better in the next day or two. If not beter after 7 days, see your dr. For an evaluation to be safe. Good luck.