Got over a cold 3 days ago. bad post nasal drip. very thick, wake up choking on it. sometimes has blood. how can i get rid of it?

It is probably a: viral infection in which case there is little you can do other than over the counter symptomatic relief. Rest, fluids, analgesics and decongestants. Most colds are three days coming, three days with you and three days leaving. So you have about three days to go. If the mucous turns green it may mean a bacterial superinfection in which case you should see a health care provider.