Undergroundbarbie, welcome to MM!
Dancinggirl is right. From my own personal experience, the only kind of HRT really worth taking is transdermal, bio identical gel (my preference) or patch used with bio identical Utrogestan, preferably used vaginally. It is also worth noting the the all the risk elements of taking HRT are in the synthetic progestins (this does not include Utrogestan), not the bio identical, transdermal oestrogens. This is why I feel so strongly about this issue and why I think GPs should be precribing it.
I'm not surprised that Prempak C gave you headaches, it doesn't have enough oestrogen and contains the dreaded progestin. I have tried the lot and I was on Angeliq for quite some time but it gave me headaches, bad dreams and didn't work because it was far too weak (not enough oestrogen) but I never had a bleed while taking it. The progestin used in Angeliq is supposed to be better than some but it still gave me silent migraines and in the end I started topping up my oestrogen levels by bunging on a patch but even then it was only just about passable and I certainly would not recommend it.
I then changed to the oestrogen gel and never looked back, it worked immediately and my temperature control went completely back to normal along with everything else. I now regret the time I wasted taking the wrong medication and hope that others can learn by my mistakes.