I'll tell you what my experience was with knee trouble, but I am not suggesting that this is your situation. Besides the bike fit you really should have it looked at to determine exactly what the problem is.
On my first tour I took on too many hills too fast, was riding with platform pedals and no toe clips, wasn't doing any stretching of the quads, and after 5 days in the saddle screwed up my knees so bad that I couldn't ride for 6 months. Sounds the same as yours - sharp pain right across the top of the kneecaps. Tendonitis was the diagnosis. After seeing a physical therapist and following his recommendations (repeated icing of the kneecaps, stretching of the quads, 10 days of ibuprofen), I was finally able to ride again - short distances at first, but eventually (over several months) back to my normal 30-miles per day.
I'm not suggesting you follow that advice as it is not clear that you have the same issue I did. Get it looked at. One thing I will say for certain - don't continue to ride with that pain, as you might end up like I did - 6 months out of the saddle.