I have been playing for about 10 minutes and then i tried to play low d to C and it would play low c it just squilled!! help me please

sounds like a screw came loose or a spring came off a post. take it to a repair shop and they should be able to find the problem easily and fix it pretty cheaply

This happened to me when my Forked F vent key wasn't sealing. Take your oboe to a repair tech.

As Prettybird says it could be an adjusting screw (or even a pivot screw which holds a key on) has come loose or it might be a silencer cork fallen of from between a screw & the key. Another possibility is that a pad has compressed a bit & not sealing.

Oboes are complex machines &, like cars, go out of adjustment over time - those padded with cork pads are particularly prone to this. This is why it is recommended to get instruments checked out every year or so - a technician can pick up things that are going out of adjustment before the player notices & has a panic. The trouble there is that many techs do not understand oboes either! So get recommendations from other experienced oboe players or tutors.

Because of the complex linkages blindly attacking adjusting screws with a screwdriver if you don't know what you are doing can make matters far worse.

Good luck