Do I qualify for injured spouse relief?

OK, for the last 4 years I have been in the most awful marriage ever. He has worked a total of 4 months out of the last 4 1/2 years....(& they are not even in a row!). I have held a steady job the whole time & the IRS has taken his past due child support out of "my" refund. We always do married filing jointly. I am divorcing him because of all of this....I am sick of it!! Over the last 3 years they have offset 6415.00 total. Will I qualify for injured spouse relief? If so..can they go back for the last 3 years? Please someone help!!