Hope you feel better, Cathy. I, have had the same experience many times. I feel better while riding, but I pay for it dearly, later. I have learned my lesson, after enough times of getting a sinus infection, bronchitis, etc. from what started as allergies.
I have been fighting the pollen for a week; usually pollen isn't an issue for me, but I had to start taking Claritin in addition to Flonase this week. Wednesday night, I started getting a headache in class and felt really awful by the time I got home. I had gone for a run in the AM, which was dumb. Yesterday, I felt like that same truck had rolled over me, and it took me awhile to get out the door. I wanted to ride, or at least go out for a walk, but thankfully, it rained, so I rested. I am better today, heading out for a group ride. I'd like to go with the "spirited" group, but I know that would push me right back over the edge. I will be happy to do my 30 miles with the slowpokes, because I still am not right.