My boyfriend was sick throwing up 3 weeks ago and today i just threw up. did i get sick from him?

Gastroenteritis: Stomach bugs could be viral or bacterial, which is dependent on the cause. But for sure, oral contamination of any foreign body is a possibility but the time of incubation til the time of manifestation of clinical symptoms is usually less than 3 weeks. Make sure you increase your fluid intake for now and if not better in the next 48 hours, probably should see your physician.

Gastroenteritis: While there are many causes for throwing up, the most common cause of an illness which one is throwing up is gastroenteritis, and that is usually viral. Viral gastroenteritis can be quite contagious, but the timing of transmission is most likely to be within a couple days of exposure. If you are just throwing up now, it is very unlikely gastroenteritis that you got from him