Ask your GP for another type of HRT. There are plenty of them, swinglish although there are supply issues for some and some are being discontinued. GP's and some meno consultants swear they are all the same but from reading this forum you will find this clearly isn't the case. What suits one women won't suit another as I found out. I tied 5 types of HRT over 3 years before I found the right one which controlled the symptoms and left me with a couple of side effects I could live with.
Stopping and starting is no good, it just confuses the body...why suffer that way when your GP can give you other things to try.
Conventional wisdom says you must try anything new for a full 3 months to see if it settles before changing to something else. It depends how quickly your body responds. Mine took 5 months to settle on the regime I fine the best and I now have at least 90% of my life back.