What, like 2 weeks continuously? I'd have thought you'd be pretty tired as well!
But seriously -- the idea that sperm makes women tired is a bit, um, unusual. Although if you believe that is the problem, you could try either using condoms or having a vasectomy.
Otherwise, maybe you should consider that perhaps the sex was great for you, but possibly not quite so great for them that they wouldn't actually like to get a bit of sleep every now and then.