My husband did not pay taxes for years. I did not realize I could file separately and now they are garnishing my wages for his back taxes. Can I go back and refile those years sperate from him?

No, you cannot, because filing jointly is normally an irrevocable decision.

However, you CAN amend the return and request status as a Innocent Spouse, which should relieve you of the garnishment action.

You probably should contact a local enrolled agent to review your case and represent you before the IRS to get this mess fixed.

On the joint return, both the spouses are jointly and severally liable for the tax on the return, and interest and penalties. Even when only one spouse owes the tax, both spouses are liable for the full amount. Before the due date (including extensions) either spouse may revoke the election to file a joint return. After the due date (including extensions), the joint return can not be revoked. Your U.S. Tax Return: Filing Status for Married (http://taxipay.blogspot.com/2008/02/filing-status-for-married.html)

For your options, you should read IRS Publication 17: Your Federal Income Tax; Chapter 2 Filing Status; Married Filing Jointly; Filing a Joint Return -- Relief from joint liability.