I have cancer, and am on chemo, my doctor prescribed budeprion xl...

hmmm... Doesn't make much sense to me. If you've got no appetite and some depression going on (which would be totally beyond normal for someone with cancer), I'd go for mirtazapine/Remeron. It should increase your apetite and help you sleep. If you need more energy, modafinil/Provigil might be a good choice as it tends to focus more on wakefulness than other stimulants. Of course, whoever is prescribing your medications needs to take into account the chemotherapy you are on when making decisions, but bupropion seems like a poor choice for someone with a poor appetite.