What is this under my armpit?

So for about 2 weeks I've been having this lump under my armpit and just last week it started to get serious. At first it just looked like a infection and I've dealt with infections before so i squeezed all the pus out and it was A LOT of pus and blood by the way. So after i do that I put some ointment on it and wrap it up. For a day it felt much better but now it is not only much more swollen and hurts just as bad if not worst then it did before but there is like a huge bump internally and I'm sure it's a cyst. So now i tried and tried to squeeze out any pus but there is simply nothing there but i feel a lot of pain and it feels really warm but it doesn't stink like a infection would and no pus is to be found so far. What could this possibly be?