I get the same thing, and also when I shave my ass. I've managed to deal with it by doing the following:
1) Use a high quality cream for sensitive skin, and apply liberally
2) Chemically exfoliate the area before shaving, and apply to the area once every two days indefinitely (or until bumps have cleared)
3) Shave slowly and with the grain (you can go against the grain once your skin gets used to shaving)
4) I recommend using a single-bladed or double-bladed razor for sensitive areas. It'll take more time, but you'll have more control
5) Shave more frequently. I'd venture to guess you don't shave very often based on the picture you've sent.