I started to feel "off" and really nauseated. I was wondering if maybe I was drinking TOO much water and bloating myself...I limped home and had to "steal" some extra water from a municipal building's spigot on the way home. When I got home it was clear that I was borderline dehydrated and had not had enough fluids in me.

It was "only" a 2 hour ride but I went through 3 bottles and still got overheated and borderline dehydrated.

I just re-read this part of your post. For me, a classic symptom of heat exhaustion is feeling like you've had way too much water and feeling bloated, and also the nausea. This is one of the ways one gets into trouble. You feel like you've had too much to drink, so you stop drinking, which then makes you even worse. I suspect you're way more than borderline dehydrated. My prediction is that you'll be wanting to drink water all day tomorrow.