Could I apply for citizenship and when?

It depends on many factors, like possible convictions and travels outside of the US. But you should have been able to apply in 2009.

Generally, a foreign national who has been a Lawful Permanent resident (has had a "Green Card") for five years may be eligible to apply to become a naturalized citizen (and even may file the application 90 days before the end of that 5-year period). There are many other details that also address eligibility for naturalization, and it would be wise to work with an immigration attorney who, after learning all of the relevant information about you, could advise about eligibility and represent you in the naturalization application process.