Can Slight Enlargement In Brain Become Tumorous?

Hi I first went to my neurologist because of constant headaches. It was every single day lasting about 8-12 hours. I did and MRI and they found out that there were white spots on my brain they also found that my head is a little bit bigger than usual people from the same age. One side of my head is bigger than the other and inside on my Cerebral cortex one was a lot thicker than the other. The doctor said I didnt had to worry about it but he said also that I need to do MRI every 6 months to see how things are going as he said it isn t any tumor or MS but he also said that it s better to keep an eye on it in case it might turn into a tumor. Should I be worried?