Hi @MeganM,
You certainly took a lot on yesterday! gym and going back to work! as @zoffiel said anything unusual let your doctor know, although a good guess would be just organized for work and going to the gym would have tired you out, I do know that the combination you are on does cause fatigue, however we all respond differently to the drugs we are on, there are several ladies in the metastatic group who are on the same drugs as you, perhaps they might read this and put up a post about how they are going,try not to put too much on yourself,going to work full time and doing metastatic breast cancer is a hard enough gig as it is!
wendy55