Shop for another oncologist and get a second opinion.
My spouse (doing follow-up chemo for colon cancer after surgery) is doing only Xeloda, but he was feeling extremely run down, insisted on last appointment w/hid oncologist that several blood tests be added to their nromal test list. Doc was a bit annoyed but added them - testosterone, a couple of enzymes, etc. Tests came back - way low on testosterone (normal range 30-80 or somethign, he registered at 7!). So doc finally paying more attention to looking outside the box on his chemo treatments and patient monitoring, and prescribed accordingly. He's listening to my spouse, who's been doing a lot of homework on all this.
You are your own best advocate. If you can tell something's wrong, follow up until you get a doc who listens and responds.