I have, and have had for the past 2years a problem with my imune system. Started on day when my tongue just swelled up.Not eaten anything different. 2-3 days after, i was run down like i had flu. This kept going on every couple of months. Been to doctors, the ENT at hospital and then to dermatology. Dr there is great and has looked at all different types of things that could be setting it off.
I still have it now and its still ongoing. I'm in next month for nerve testing to see if they're shot. Also found out i had a crappy liver (blood tests) AND recouring glandular feaver (hence feeling like crap for weeks on end).
So far i have changed my diet and this has (we think) decreased the number of bouts i have. I also carry Max strength cold and flu tabs about with me at all times. As soon as i start feeling like anything is going to start, i get throwing them down my throat. Not ideal but tends to keep things at bay. I still ride but not as much as i want. I have to sleep after a ride(in the afternoon) and like nbt says, keep eating little and often.
Good luck with it…we know how you feel!!