I Have Been Experiencing What I Can Only Describe As

I have been experiencing what I can only describe as symptoms like coming down with flu in my head, that is, lethargy, throbbing, dull, tired sensation coupled with a swimming in a whirlpool sensation, not dizziness, but I get it after each time I mow the lawn, accompanied by a chronic shortness of breath and it could take me 48 hours to recover. I suffer from hay fever, tinnitus and rhinitis but yesterday I got the symptoms after doing light housework. I am 54 and told my doctor about it last year but she dismissed as getting older and running on empty. I am afraid it could be something more sinister
Thanks