jeeper, my dad had issues like you are having.
Something I learned from it... many doctors are not that motivated. If it doesn't start getting better soon, push them to take cultures and find a more appropriate antibiotic. My dad's doctor just kept giving him more of the same stuff. It wasn't doing anything good at all.
They were talking about removing lots of his foot. Fortunately for my dad, his doctor got sick himself and took a couple months off. The doctor who was filling in took one look at the foot and the prognosis, made a comment about the capabilities of the regular doctor, took a culture to properly identify the problem, changed to a different antibiotic (a "newfangled" on that the other doctor had not cared to become familiar with), and a lingering-for-3-years infection that went to the bone went away and healed completly in 2 months.
If your doctor is on top of it, awesome.... you found a good one.
Just remember that the person that is really responsible for your proper health care is you.