I know you don't want to hear this, but changing the terms of custody in NC can be one of the most difficult and expensive legal proceedings.
You definitely need to talk to a local attorney, because your ability to do any of the following depends on what legal orders have already been executed in your case, and how long it has been.
The first hurdle before a NC court will consider whether to give you more custody time is that you must show there has been a substantial change in circumstances since the last court custody order. There is no hard-and-fast rule as to what counts. Starting school, or starting a new school might count (or it might not). Ditto remarriage and a new family, or significant change in family income or employment.
If you convince the court that there has been a substantial change in circumstances, the final hurdle is to convince the court that giving you more time is in your child's best interests. I gather from your question that the court has already considered your case and decided that a 50-50 split is in your child's best interests. You will need to convince the court that the situation has changed and the environment at your house is better than it was last time (or the environment at dad's house is worse).
Child custody professionals often recommend that school-aged children need a "home base" to succeed. You may find that retaining such a professional to evaluate your situation helps the judge understand better what is best for your child. Good luck.
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