suep112 is right.
Graves without beta blockers when needed is a deadly potion.
I used to cut my Inderal into qaurters as a 1/2 of one or a full one was too much for me and would drop my pulse and heartrate too fast.
But taking 1/4 of one or half of one when needed...eased the symptoms.
Beta blockers are actually well known for helping the FT3 to lower.
Since you have graves, have you been treated for your rapid heart beat? Have they checked your pulse rate? I needed beta blockers to calm down. You might ask about this. Almost everyone with graves has anxiety and a rapid pulse. Until your levels are correct, you might need something for your rapid breathing...could be related to a fast pulse. Just a thought. Good luck to you.
Sounds like you may be going hypo from the carbimazole (Neomercazole).
I suggest you call the Endo and ask for labs to be done.
Most Endos will tell you that it takes 4-6 weeks to get a correct dosing of either anti-thyroid meds or thyroid meds.
That is utter garbage.
I used to go from hyper to hypo within 2 weeks each time when I was on Carbimazole.
I am the same with thyroxin now.
Get your levels done and you will find that as you still have your thyroid, have Graves...that your TSH will still be low (as it never budges with Graves and a Thyroid)
and that your FT3 and FT4 are low which means heading hypo.
Any cold symptoms?
Constipation?
Aches, pains etc?
Dry hair, mouth ulcers?
What dose are you on and how long since your labs?
Debs (RAI & TT 2008 - Graves,Hyper & Thyca)