1. "should I just start from scratch??"
...no, No, NO.!
2. Stop overfeeding. Yes you are. Feed nothing for a few days. Nothing.
Then feed a lot less than you were.
3. Don't clean the filter materials. If they get dirty fast, you are still overfeeding, stop it.
4. Do not buy more fish, just let the tank run.
5. Do gravel vacuuming with small water changes, 30%, about once a week.
6. Use Amquel or Prime on any new tap water when you do water changes.
And, ,,, Put a dose in the tank right now. It will help detoxify the ammonia.
Note: your ammonia test won't always give accurate results when using some water conditioners.
AND some products can screw up the cycle process. Filter materials which contain zeolite are often sold to new aquarium owners to control ammonia, but they only delay getting the tank truly healthy.
Run a tank with very little food for two whole months and any problem with ammonia and nitrite will go away.