Training & Nutrition - Wierd temperature spike after riding

Lately after riding my body temp has been spiking. Even though I've cooled down completely and showered hours before I begin to sweat again and start to feel "sick." This happens about 5 or 6 hours after riding and usually after my weekly long ride (70-80 miles). Eating or not eating doesn't seem to make any difference and my rides have been this length for over a year with no other effects prior to this starting.

I feel fine until it happens but once my temp goes up I feel exactly like I have a cold or the flu. Sweating and feverish. Sometimes with light nausea and I definitely do not "feel good." My normal temp is 97.8 which is a bit cooler than average but it's my normal. The last time it happened my temp was a bit over 99* several hours post ride. This lasted throughout the night until morning.

Is there something going on here that I need to worry about? Or is there something I'm not doing that I need to be doing to ward off this post-exercise rebound? It's been getting worse after each ride for the past 2 months or so. Nothing before that.

The ouija board says, "low blood sugar." I'm suggesting that your body's continued synthesis of glycogen after a long ride is scouring out your carbs, and leaving you with depressed blood sugar levels. Caused by insufficient carb injestion.

I would suggest a schedule like this after a long ride:
10 minutes: Recovery drink. 1g (4 cal.) of carbo/kg body weight, plus about 25g protein.
Next hour: Another 50g carbos, a little at a time, could also have a little protein and a little fat. I like a dark microbrew, taken with laughter, followed by a bagel with cream cheese.
Then a normal dinner: 1/2 plate of veggies, 1/4 plate carbs, 1/4 plate protein.
Bedtime: 15g whey protein is nice.

As to why this is starting now? Any change in diet or circumstances? Normal diet percentages too high in carbs, too low in fat and protein? Not enough veggies? Too low body fat percentage? Those dietary choices accumulate.