I hope I'm not sick!

I did a 50 mile training at Yankee Springs on Sunday, all single track.  I did this in preparation for the Syllamo 125K in Arkansas in 2 weeks.  During my ride I found it hard to take deep breaths of air the longer I was out there.  By the time I was done it felt like an elephant was standing on my chest.

I talked with my coach and he said that it was probably just the fatigue staring to catch up with me.  I have pushed my limits which is good, but I also need to watch it to avoid getting seriously sick.  When you get to fatigued it can lead to respiratory infections which is what I thought I maybe coming down with.

Just to make sure I went to the doctor today to get checked out.  He listened to my lungs and checked my ears.  Nothing really showed up.  Just to make sure he had chest x-rays taken and those came back negative too.  How ever he did find fluid in one of my ears and prescribed antibiotics as well as rest and drinking lots of fluids.

So what caused my breathing to feel the way it did?  Not sure, other than I hope is is just a little fatigue and I need about 4 or  5 days of rest.