I've been shaving with a straight for about 2-3 weeks now. The blade is ultra sharp and I have no problems on any part of my face. I don't even have problems shaving my neck and under my chin. However, about 15 minutes after I finish shaving, the area under my chin develops razor bumps and is extremely sensitive. Aftershave helps a little but not by much. Any ideas or suggestions.

I don't experience any kind of pulling or discomfort during the shave. I have been resorting to using my Gillette Pro Fusion 5 blade razor on my neck and shaving the rest of my face with the straight but I would like to eventually get to the place where I can toss the Gillette.