Low EF on Co Reg with questions

I'm a 37 year old cancer patient who's EF dropped to 15 thanks to either the chemotherapies I've been on for the past year, or possibly a virus.

The cardiologist started me on CoReg (3.12 mg 2xday), Lanoxin (.25 mg once a day) After a week, I still felt like crap, so he put me on a diuretic (1/2 a pill every other day.)

After two weeks at that dosage level, he doubled the Co Reg dosage and I feel like crap. Vomitting, sinusitis, coughing, I can't get warm.

My oncologist thinks my heart will recover rather quickly since we've stopped the suspect drug, but I'm wondering if anyone else had similar difficulties on these meds.

Thanks,

Chris