I Recently Visited The Caribbean For Vacation (early Nov), Followed

I recently visited the Caribbean for vacation (early Nov), followed the next week by a business trip to Brazil. While on vacation, I walked excessively in barefoot or flip flops, and noticed a pain in the left foot in the arch. This has continued, and actually gotten worse. I cannot pinpoint when, but since the return from Brazil, I noticed discomfort on the top of my left foot, and felt what could be a very small bug bite. Although the bit mark eventually disappeared, redness replaced it and spread down my foot, essentially following the blood vessel. It is now extremely sensitive to touch and quite painful on standing. Combined with the pain in my arch, I find it difficult to walk. I went to a local clinic, and they prescribed an antibiotic. I have been taking this since Sunday. The symptoms have not gotten worse, but have not improved. Plantar Fasciitis for the arch?? What in the world is the infection?