The car shifts roughly. Sometimes it won't shift into the next gear unless I let off the accellerator. This doesn't start happening until the engine is warm, usually after I drive about 10 - 15 miles. Also when this starts to happen the check engine light comes on when I stop the car and goes off when I touch the accellerator.

When your car's engine is cold, the computer knows this and trys to give it all the fuel, air, and advanced timing that it needs. But as your engine warms up, the engine's priority turns to getting good emmissions along with efficient performance. So any one of the items I've mentioned could be failing after the engine warms up. Eventually, whatever causing the check engine light to come on briefly, it will cause it to come on permanently. You definitely need a mechanic to take a look at your car and drive it around so he can see the check engine light come on. The heat from the engine may be affecting the crank angle sensor, and that will cause the computer to think the timing is off. A mechanic should be able tell once they start inspecting the car's systems. Hopefully it will be an easy fix for them.
Good luck!