Pain in face and sinus problems

Hello, I had a root canal on tooth 14 about three weeks ago.  The specialist said there were no signs of infections, but my tooth was cracked in two places and the root canal was performed for that reason and because I had a large sensitive filling in it.  After the root canal, I was given a permanent filling and am scheduled to be fitted for a crown this coming Monday at my regular dentist office.
Ever since the root canal, from the bottom of my jaw and up to my eye, on the left side of my face, I have been having excruciating pain.  I have never had pain like this before.  My famirly doctor says I have a sinus infection and I am on my third course of antibiotics.  I have had many sinus infections in the past but the pain has never been like this!  It hurts to chew, suck on a straw, swallow, move my neck to the right, and talk.  Lortab 5 pills only subdue the pain to a bearable pain.  Most of the pain seems to be in my cheek area and near my ear.  The pain started to subside about four days ago, but it has returned with a vengeance.  
I remember the endodentist giving measurements and my fourth root was a length of 30, much longer than the others, 17-20.  Could one of my sinus cavities have been perforated and could that be the cause of the pain?  Do you have any other ideas as to the cause of the pain?  This pain is so bad I have not been able to work for the past two days and I don't know what to do.  I have seen two family doctors and both think it is related to a sinus infection, but it just seems odd it started with the root canal and I have never had pain like this before with a sinus infection.  PLease Help!!!

[mcpeak4]

I had tooth #3 that was cracked and then refilled with a new filling, they ended up having to do a root canal. I developed an infection that started in my gum and went up into my sinus cavity. The whole side of my face was swollen and I was in extreme pain. They put me on Amoxicillin and then tried another RX, I can't remember the name of it, but the pain continued. I ended up going to see an oral surgeon who put me on Augmentin, it took the infection away but needless to say I lost 2 other teeth and have bone spurs in my gums now that are causing me problems. This has been a 9 month ordeal. I am just a regular person, but nothing seemed to work for my infection but the Augmentin, if you haven't tried that, I would.  Hope this helps!