Hi over the last few weeks I find I m getting fatigued really quick. I mow lawns and I can normally last all day but it has gradually decreaseing to the point were today during the first lawn I had to stop twice. I went home for a couple of hours then went to another job and 5 mins into it,it got that bad it was like I had done an hour work out and was about to faint legs shaking and all but I had done nothing really. What could it be and should I do thanks Greg