Does Tibolone tiredness stop??

I have been taking Tibolone now for a few weeks, it has done everything I wanted in terms of improving my symptoms, but I have an overwhelming tiredness, I cannot keep my eyes open some days. I'm not really old (40) and taking it due to total hysterectomy, so I don't think the tiredness is age related, especially as it only started a couple of days after commencing the medication. Has anyone else experienced this, and if so did it subside and how long did it last for? Thanks in advance ☺