Getting hacked?

Recently I noticed someone on my email address trying to change my maplestory info.. I don't even play the game anymore but i'm concerned that someone got into my email address. I'm assuming there's a keylogger on my PC, is there a way to find it and remove it somehow? I have avast antivirus but it's mostly useless and doesn't detect anything even when i'm suspicious I have malware

EDIT: I typed this up in a hurry but i'm looking for a step by step guide on how to clean out my PC.. so I can change all my passwords around freely without worry

Try using Malwarebytes.

SuperAntiSpyware works good too.

Microsoft Security Essentials is good too and is also free.

It would be nice to know what e-mail provider you use, gmail for example register the IP adress that access the account, you can check them at the bottom of the e-mail in a link that says details, that way you know if your e-mail was compromised.