With a name like RoadHoe, one could guess what might contribute to the smells......
Quite a variance in what it could be, as you see from the drastically different replies here (beyond washing your backside). To me, I read this as a stagnant odor in the interior. Meaning you open the door and get in (without the vehicle running at all), and you get the sense you've 'dutch ovened' yourself. If I'm reading your description correctly, it could be something as simple as a clogged drain for your evap box. If that gets clogged, it will pool moisture and end up smelling like the 2girls1cup video inside. And its only going to get worse as the temperatures go up (if this is your culprit). Fairly easy diagnosis, or a quick check anyways. Just let your truck idle with the AC on, and check to see the evap is draining properly (that infamous dripping, clear liquid you always see underneath a ridling vehicle in the summer).
If it is a clogged drain, you might need to douche the evap box to sterilize that RoadHoe, in a sorts to get rid of the evidence you had the clap. There are some fogging machines out there that will help a lot, for a simple attempt to fix it. We often drilled holes in evap boxes and used a pressurized spray can, filled with diluted Mr. Clean (we used a plug to seal it when done). Several ways to clean the scabies....