The Hyperplasia mentioned above, I suffered from that, Tamoxifen induced and it came on pretty much at the start, within the month of starting Tamoxifen. After two surgeries and 2+ years I came off Tamoxifen. As to the joint pain that also came along!
The brand I had taken was Sandoz and the link here is their explanation including side effects
https://www.mydr.com.au/medicines/cmis/tamoxifen-sandoz-tabletsNot everyone suffers what I did
Perhaps a visit to your GP for a discussion before your Specialist appointment may help resolve what it is as we are all different in how our bodies metabolise medications and reactions et cetera
Take care