Don't worry. Even if you did have lice, you wouldn't have to cut your hair off. But you don't have lice. You say you shampoo near the scalp and the spots start about 6 inches away? And basically, the hair from there down gets nothing but conditioner and linseed gel?
I'll bet you can guess what I'm going to say next. You've got build-up. Shampoo from scalp to ends, and your hair will be fine.