How funny that there are more people who get tachycardic! I also get breathless -- I kept getting handed inhalers for 'exercise-induced asthma' before they figured out it was my heart. I guess because all the breath tests showed fine lung capacity, they concluded it was only when I exerted myself that I had it? The inhalers did nothing, of course, because it wasn't that my airways were constricted, it was that blood was moving through my lungs too fast to pick up enough oxygen.
I can't think of anything in my life that coincides with the onset of the fatigue. A year before, however, I had a really, really horrible time at work with a woman I can only describe as a sociopath. It was a very stressful time, and I got facial ticks and pain in my hands and feet. Can there be a lag to the effect? But I really don't want to credit that terrible woman for this lasting effect on my life.
I really relate to the emotional thing -- I often find myself near tears and the only reason is that I am so tired. If DH asks me what's wrong I'll start crying and say, "I just want to sleep!" :( Got that like yesterday, with happy little DD babbling away and climbing all over me, and all I wanted was some rest.
Oh, fuzzpig, I hope your UTI clears up and that nothing else is a problem 
Really glad your DS is loving nursey, helibee! And congrats on the job, altogether!