Warwick, my heart goes out to you truly!
In my opinion? I would probably check in with your GP if this persists over the weekend. I know we should expect 'ups and downs' but I'm just putting my sensible head on here!
You've had a couple of migraines since starting Tibolone? Good idea to mention these to the GP! I know it's early days etc. etc. but if any symptoms no matter what causes them are making you feel that bad, it's important to get checked out if only for reassurance! If anything gets particularly worrying, don't hesitate to call 111 and get seen by the out of hours GP.
As a note, my BP is now starting to dip worryingly low. It's down in the 90/60's a lot of the time, and this makes me feel very confused, panicky and sick - not to mention dizzy! I had one day when it was ok, but yesterday from teatime onward (even after eating) and today it's been VERY low again. I'm keeping a close eye on the situation......I don't even get this low on no HRT!

I know Mer over in the surgical menopause thread has been on Tibolone 11 weeks and has experienced a lot of dizziness and other symptoms progressively after a few weeks (but it could have been post-op hormone crash in her case), but I would have thought the Tibolone would have worked to alleviate that by now if it was a sudden drop in hormones. She was off to her GP yesterday to get checked out, so I'm keenly waiting to see what her update is.
So I guess I'm saying, Warwick - if you're feeling truly rotten, get checked over! It may be the Tibolone, it may be something else entirely but the important thing is if you're really not feeling well then having a check over can at least put your mind at rest - there's no harm in it (especially as you're hypothyroid as well. I know Tibolone raises T3 and T4 slightly, so something might need tweaking there - you never know)!
Sending you biggest hugs, and do check in with us when you've taken your dose today if you can so that we know you're ok! After all, you're a sister to us all here! xxxxx