It's not a reliable method at all. I mean it's a reliable method to get hospitalized, not reliable to ctb.
If it's a cry for help, I hope you will find an option to ask for help without harming yourself. With modern sleeping pills you can just fast forward to getting admitted voluntarily by saying that you feel like doing it. The result will likely be quite similar minus the puking and/or stomach pumping. You can call a hotline and tell them that you want to do it, and get transported to a hospital.
If you want to ctb, I'm not going to try to convince you not to. I do respect this choice, that's why I'm here. However this post really gives the vibe of someone who wants to get helped rather than ctb. This site is full of resources about reliable methods. With unreliable methods it's not worth it in my opinion.
I hope you're an adult, it sort of reads like a post of someone who isn't an adult. Please reconsider, having many attempts usually makes ones life significantly worse.