welcome to HCM,
the symptoms of breathing difficulty, pain in chest, heart, legs may all be secondary to the amount of blood loss you are having due to heavy and irregular bleeding. but still you need to get investigated thoroughly to rule out other causes.
presently what you need is to stop this irregular heavy bleeding as soon as possible. you need to visit a gynecologist to help you.
what you are suffering from may be dysfunctional uterine bleeding
or may be the after effect of removal of mirena
take care and get well soon.