Help- Lumps under skin?

About 3 weeks ago I developed a lump on my left left right by the ankle bone, it appeared red in color and raised, it was the size of a dime.  I ignored it assuming it was nothing and over the course of 2 weeks the lump got larger (size of a dime/quarter) and my entire foot started swelling.  I then proceeded to have another lump under my right knee cap (size of a nickel).  Both of these lumps were tender to touch, red in color and somewhat painful.  They both were hot to the surface.

I went to the doctors and they assumed I had a bacterial infection that my body was fighting.  I went on antibiotics and the lumps did not go away.  They also discovered I had poison ivy on my face and therefore started me on prednisone.  I was on the medicine for the so called bacterial infection along with prednison (my lumps started to slowly dissolve and go away).  At this time they also tested me for lyme's disease which came back negative.

This was about 2 wks ago and I woke up this morning with another red lump on the inside of my right foot (exact same as the one I had a few weeks ago but in another spot).  It is painful to touch and right now the size of a dime....I am sure it will continue to get worse.

I am concerned that this is not a bacterial infection (as I am not sick) however that there is something else going on that I do not know about.  No one seems concerned but myself.

PLEASE HELP/ADVISE!