Feeling very tired and flat while on test e?

[nusa]

Im into week 4 of my test e cycle, my first few wks I felt great and had energy to burn and was basically jumping out of bed of a morning.
But for the last week Iv been very tired and flat and not much energy 24/7. finding I'm needing naps in the arvo which has never been me at all.
Is this a stage normally associated with running test & will it pass? Im doing a 4 day split at the gym so I dont feel like im overtraining at all, also my diet is dialed in, but basically I still feel like shit and Having to force myself to train