gasoline smell while driving?

[buffalogirl]

I have a 2007 Yaris sedan and while driving the other day my car smelled like exhaust/gasoline. I thought it was the big truck I was next to but it is still happening (almost a week later). It does not smell when I get into it, but after its been running for a while, it starts to smell. Fortunately it is starting to warm up here, so I can open the windows when it starts to smell, but it happened again today and I now have a sore throat from breathing it in (even though I rolled the windows down) and when I got to work this morning a coworker commented on how I smelled like gas! Any ideas on what could be causing it or how to fix it? I can't take it anywhere until tomorrow, so I'm hoping its something easy that I might be able to do in the parking lot or at home. Thanks!