Flu rarely has runny nose or very sick tummy. Although it might be a virus of some sort. Is your muscous green when you blow your nose? If green I say you need an antibiotic. You say sweats, does that mean you have a fever? Keep your fever down and give it 4 or 5 days, see if you start to feel better. Flu starts to feel better within 5 days. Unless you suddenly take a turn for the worse, then of course go to the doctor or emergency.
I think it is possible it is a bacterial infection, and your tummy is sick from the phlegm going to your tummy. Try sleep with a lot of pillows, almost sitting up.
To make yourself feel better cough medicine, buy DM. Do not buy cough medicines that also have medicine for stuffy head and fever. You should always take all drugs separately. For the congestion you can get a decongestant/antihistimine (the only combination thatis acceptible in my book) and for fever and discomfort ibuprofen is magical.
Edit: I just thought to ask if you are able to get out of bed, or if you are completely exhausted, impossible to function. That would be the flu. If you just feel like shit, but can still get up and work, no way you have the flu. More likely a sinus and lung bacterial infection.