I forgot my email and Origin password

forgot my Email Address, Username and Password but i know my serial key that i used

you'll need to contact CS for help with this since this is a public forum we cannot help you since it would involve accessing your account

They can be found here: https://help.ea.com/contact-us
Choose a category, a game and a platform for the contact options to show up.
If live chat is gray, change your country to US and make sure you're on US Business hours. It might also gray because they're very busy. Try later.
See this post if you have trouble with the site: http://sims3.crinrict.com/en/2012/10/how-to-contact-ea.html

 sign in with the username and password you used to post on Answer HQ (click on Login in the top right hand corner), and follow the guide to ask your question. If your issue cannot be solved from our FAQ list, you’ll then be prompted for ‘Product’ (enter Sims 3) and then for ‘Category’ (select ‘Account Management’), you can then select 'I still need help' and depending on the time of day and your geographical location, you'll be prompted either to send an email or to initiate a live chat with a game advisor     please include as much detail as possible, so they are able to answer you straightaway