Firstly, don't panic. Your Switch isn't broken. It can just be finicky and confusing. Do you have autoRCM enabled? That can make it difficult to tell whether the system is off or in recovery mode (since the screen doesn't turn on in recovery mode unless you inject a payload). So you may be turning the system off whenever you think you're turning it on or vice versa. Make sure you're dongle is charged, plug it in, and hold the power button down for 10 seconds. If that doesn't work, wait 10 seconds and try it again. Pay attention to the led on the dongle to see when it senses the Switch power on. If the system needs charged and you have autoRCM, hold the power button for 12 seconds after plugging it in and then just let it sit for 5 minutes before trying to inject a payload.