I am so sorry for what happened with your dad, that's an awful thing for anyone to go through.
But please do not worry about the unpredictable bleeding following a change in hormone therapy.
This is a normal response to fluctuations in hormones and an extremely common experience following a change in treatment.
It doesn't require medical attention unless there is persistent irregular bleeding more than 6 months after changing HRT.
Untreated women also frequently experience menstrual irregularity in perimenopause anyway.
Look after yourself and focus on what's important to you.