Like the others said, it could be the razor. I nicked myself on the top awhile back but it just does'nt seem to heal, however i find that when shaving that part i go over it very lightly and it still shaves smooth.
It could also be the way you are holding the shaver, as i tend to catch myself just above the ears in the awkward spot as i have to angle the razor to shave correctly between the gap.
I'd probably go for a shaver with 4 blades or as the others said the Gillette fusion, im not sure where i read this but isnt there a vitamin e cream or something for the cuts?