Make sure your razor is clean and not too worn out. Skin
and finding a razor that is gentle enough, but also cuts clean enough is a process. I use Venus four or three blade razors, and go slowly because when i have rushed in the past, bad things happen. The pimples you are referring to could be ingrown hairs, which hurt real bad, or they could be where your skin has been irritated, and in that case, you gotta wait it out.