I suffer from bad fatigue/lethargy, and have thought that finasteride might be the culprit (after all, it does suppress a powerful male hormone).
But there are several other factors that could be responsible for my tiredness all the time (lifestyle factors, other medical conditions I have etc..) so I can't 100% pin the blame on Finasteride. I've resigned to the fact that I'd rather have hair and be chronically tired than vice versa.
I'm also considering to ask my doctor if he'll prescribe any stimulant meds (like Adderall)
as for the OP of this thread, you've only taken 3 pills, so your tiredness is unlikely related to finasteride. Although sides are more common when you first start and usually go away in time