Will my head size increase if i continue to gain weight?

Not after puberty: Your head grows fastest during first 2 yrs of life, then slows down until puberty with growth spurt. Once you're done with growth in height--about 16-17 for girls, and 19-20 for boys, your head will not likely have any significant growth--except maybe for gigantism. You are now 45, your headsize won't change even as you are growing sideway. Keep healthy and ideal body weight. Cosult doc. Good luck.