Metastatic Breast Cancer: Whole brain radiation side effects

I finished whole brain radiation two weeks ago (10 treatments) and am suffering horrible side effects. Doctor checked me out 3 days ago and said everything looks ok but I am miserable with NO appetite, feel nauseous, head feels like it's being squashed in a vice, headaches, dizzy, weak, extreme fatigue. I am taking memantine to hopefully prevent memory loss. I am suffering and feel miserable, cannot function, cannot eat. I am hoping some of these side effects will go away but not optimistic. I am age 68 with metastatic breast cancer spread to bones, lymph nodes, brain - a rather grim diagnosis. Feeling miserable.