Welcome to Gaia! ::

It's possible that you need to work on air support. Slightly arching your tongue in the back can help get the pitch up as well, but use a tuner to make sure you don't overshoot. It's also possible that your flute needs to be repaired, though if you've had it less than a year and haven't been playing it heavily, it should be OK unless you've dropped it or something is visibly wrong. Leaky pads can make it difficult to hit certain notes, but you would notice it first at the bottom of the range, rather than the top. I'd suggest that you work both in scales and in a melodic pattern to reach C. Hear the pitch. You should work on ear training - like how athletes visualize success, we try to hear the music in our heads or sometimes to sing it so that we can then play it with properly tuned pitches and intervals. Probably if you just work on air support and keeping your embouchure steady, maybe using the back of your tongue to aim the air stream higher, you'll find that a little practice will solve your problems.

does your flute have a b foot? If so, you have an extra key to help you get that c out.

also, agreeing with ashokan, send your flute to be checked in the shop. I had a leak and it made my flute so hard to play. I didn't even know there was a leak until I started taking lessons. I got it fixed and it was a million times eaiser to get certain notes out.

The golden rule of high notes: DON'T PINCH UP YOUR EMBOUCHURE.