I've got really bad tooth ache in my back tooth and jaw and swollen gland?

Serious condition. Sounds like you are having an ongoing and spreading infection that needs to be evaluated and treated right away.
See dentist asap! Get to a dentist as soon as possible for treatment of the tooth along with antibiotics if there is an infection, which is likely. Infections can spread and cause serious consequences so do not delay!
Probably infected. You should call your dentist and ask for an antibiotic. This way since today is sunday and there probably isn't an open office...You can get a jump on controlling the infection and possibly get the troubled tooth worked on or extracted. Or if you're told to wait a few days...The antibiotic will kick in and help control the pain in 36-48 hours. Earl.