Yes, I can definitely relate. I actually went to a psychologist asking about Asperger's - I'd made my first friend in years, he has Asperger's, and recognized it in me. That psychologist dismissed the idea. I was rather depressed during the first appointment, then a couple days before the next one I had a spurt of energy that lasted up through my next appointment, I was talking a mile a minute about the source of the spurt - namely, I changed my major to psychology, which had been a more consistent interest, while my previous major had much less to do with the interest that sparked it than it did with business (I'd been an international affairs major, I LOVE languages but turns out, most people in international affairs just hire a translator). I went in ranting about what classes I wanted to take what semester and how everything was all better and how now I just needed to learn how to cope next time I was down (I'd been sleeping whenever I wasn't in class, I would buy food and be too exhausted to eat it... it was very blah, and I knew I'd need to know what to do next time it happened). By my next appointment, I was in the collapse low that followed. Considering those were my first 3 appointments, needless to say that psychologist wanted to look into bipolar - and I could believe it.
I find that applies to even just regular happiness for me, though I don't know if that's a normal aspie thing. Before the Asperger's diagnosis, I thought of it this way: When I immerse myself in something, I immerse myself completely. I don't really know if I can say I have special interests so much as I get obsessive about ANYTHING I do, it's one thing that's made me worry if maybe I can't really claim the title Aspie. Anyway, that obsessiveness applies to emotions too - for me, I can't just be happy; I have to be ecstatic, so inspired and motivated that nothing in the world can touch me. Sooner or later, that has to end... and not only am I exhausted from all the energy exerted on those good emotions and whatever I was so obsessed with at the time, but I also have to be obsessive about the new emotions, which include a sense of reality and less happiness, which when obsessed over become more and more like a mini depression, which falls into a sort of fatigue. It's actually to a point where I dread good times because the most extreme lows come directly after them, and the contrast makes the low so much more difficult to cope with. I suppose that branches beyond fatigue, but for me those lows tend to manifest in exhaustion and spending every spare minute in bed, so I think it fits here? And I do know a big part of that low is just simply being tired, so I definitely experience what you're specifically focusing on as well as the rest.