that is a long season. when i first got into racing i feel like i did the same thing, just did everything and anything i could. i eventually got stuck in a fitness rut. you are on a different level than i was for sure. a lot of people feel that if they are not riding, they are not getting stronger. you actually get stronger while recovering.
my opinion? put the mountain bike away, ride with people that share the same goals with you and turn the dial way back. it's easy to get on the mtb and throw any terms of "social" and "easy" ride out the window. it's easier to do this on the road bike with a friend and really tell yourself to relax, spin and recover.
hillier is going to totally destroy you. i dont know what the date is, hopefully it's farther out, but your body needs some rest if you feel this way.
challenge yourself in new ways. i think you said you have some sort of road bike, right?
how low can you keep your heart rate?
can you spin for an hour at 95rpm?
don't be afraid to take some time off. i never feel good if i take more than 1 day off in a row, so maybe for a couple of weeks, do every other day? you will feel better soon. you can still ride, just stay away from the intensity.