Hi peaches - welcome to the forum.
I believe your GP has put you on the wrong HRT regime. Femoston appears to be a conti HRT for post-menopausal women. You are not post menopausal until you have had at least a year without periods. You need to have a regular bleed to keep your womb lining thin. This has happened to other women on here too if a GP is not that clued up about HRT. This is what it says on the patient leaflet
"The name of your medicine is Femoston. It belongs to a group of medicines called Hormone
Replacement Therapy (HRT). Femoston is suitable for postmenopausal women with at least 6
months since their last natural period."
I think you should go back to your doctor and ask for a change of HRT especially as you feel breathless. Have a good look around this site and gain more knowledge so you can put your point across. It can take a few tries to get the right HRT so don't feel despondent. The next one might make you feel great!
Let us know how you get on.
Taz x