Windfall Elimination Provision - WEP

I would consult your local Social Security office regarding this.

Here are three links which may be useful. The last is a benefit calculator (WEP version) which may be especially useful for you.

http://www.ssa.gov/retire2/wep.htm
http://www.ssa.gov/pubs/10045.html
http://www.ssa.gov/retire2/anyPiaWepjs04.htm