Changes in my hair...

Just over the past week I have noticed my roots look oily. About an inch from my roots they are oily looking, kinda as if I didn't rinse all the conditioner out. I have changed shampoos & conditioner three times since I noticed it and took extra time in the shower to rinse out my hair but it hasn't changed. I am not sure if it has something else to do with changes in food, vitamins, etc. I take my normal vitamins and nothing that I can think of has changed with my food choices. Very bizarre, I have no clue why this is happening. I wasn't sure if anyone had something similar happen or if it would be related to anything else? I am over three years out from my bypass and almost 4 months from my tummy tuck. Thanks for your help