When I was switched from Tamoxifen to Femara, I had the same side effects. I endured it for a few months, but was so tired and achey, the doctor changed me to Arimedix and I tolerate that much better. Everyone handles these meds differently. I would call the doctor and see what he/she says. No sense in suffereing when they can give you something different.
Let us know how it goes.
L & H,