My dr. says i have fluid bhind my ear. i have a big lump bhind it now. it is causing pain/headaches. i 'm on antibiotics for a cold. will that help?

Effusion : Fluid collection behind ear can be caused by allergy, infection, eustacion tube dysfunction. As to the lump behind ear could be lymph node reacting to infection, but concerning for mastoiditis. I suggest you revisit your physician antibiotics should help.

Head lump: The lump may reactive lymph node to the infection, which is all part of the symptoms you have been having. Your primary care doctor will likely explain this.