Diphenhydramine/antihistamines shortened sleep-wake cycle?

[billwright123]

I took 2 Benadryl tablets once 2 months ago to fall asleep earlier. That morning I woke up after only 6 hours of sleep (I usually get 8-9). Every day since then I've been getting only 6 hours of sleep per night, and I feel a strong urge to sleep in the afternoon (but I try not to).

How do I reset my sleep wake cycle back to normal (8-9 hours?)