Since you were awarded Post-9/11 GI Bill education benefits you GI Bill Statement of Benefits will show you how much of your benefits you've used and how much you have left to use. I suggest you view  your GI Bill Statement of Benefits.
Is there a way that I can apply for benefits online?
Yes you can use the GI Bill Comparison Tool to apply for education benefits.
Over and above the GI Bill benefits are there any other GI Bill programs available?