Honey, I know this is not what you want to hear, but please first talk to them first! Make sure you're really clear on that you've reached your limit and you need more of their attention and love!
If you still want to do this, just get a bottle of dangerous pills like Tylenol or whatever was named here before and spread them out over the bathroom sink, the floor, and your bed. You just take one or two and act lethargic or unconscious. Your parents will get a horrible shock and you do no unintended permanent harm to your body.
Just know that even when it feels like NO-one cares about you, if you open up to someone, you'll find that almost everybody will want to help you and care for you. I'm glad you reached out first before doing something drastic. Please be safe and if you want to talk, send me a PM.