Bad razor burn on bikini line. Help?

I shave my bikini line before I go out in the boat or to the pool, and I use lots of shaving cream and warm water. But no matter what I do, I always end up with red bumps all over the place. They are really noticable and I don't know what I'm doing wrong. I use Bikini Zone medicated gell every time I shave there, but that doesnt really help that much. Do you know of any inexpensive treatments I could buy, or any tips on how to avoid this razor burn? Thank you in advance. (: