I Suffer From Serious Bouts Of Need To Sleep At

I suffer from serious bouts of need to sleep at various times throughout the day.I have lower back pain and also severely constipated.I sleep at night most times. I have prostate cancer, a bloody disorder,osteomyelitis, osteo arthritis, also triple A anuerism. I am 81 years old, my medication is as follows.amitryptiline,diclofenac,Tamsulosin,doxycycline,and ibersarten plus fentanyl patches.
Why am I constantly falling asleep and suffering sweats and unsteady on my feet sometimes.