Also, try not to advance through your subdivision levels too soon. Your model is displaying a level of lumpiness that is prevalent with going through the subdivision levels too soon. You want to take your time working the lower levels to move and smooth out your mesh before you subdivide.
“Generally” you should be spending most of your time refining the large shapes of your mesh before getting to the details which is about the last 15% of your project.
If you want to fix it, go back through the levels and do some smoothing all the way up to the highest level and it will look much smoother and less lumpy.