You are using a much too small timing capacitor. The stray capacitances in your circuit layout at the THRES and TRIG pin on the 555 are on the order of 15-25pf, which is 25% of a 100pF timing capacitor. Reduce the resistors, and make the timing cap about 1nF.
You also must consider the capacitor accuracy spec, which is likely +-5% at best. You need to trim the oscillator to the final frequency. I would do this by picking a timing resistor which puts the oscillator slightly below the desired freq, and then parallel much higher value resistors across the timing resistor until it comes in. It is much easier to get a final value resistor by paralleling one which is 10% too high with another that is about 10X the first...