How do I find my tax return history... my new job is going to be doing a background check for the past 7 yrs and I have no clue what all jobs I did in the past

May be you can reconstruct on the basis of your previous years tax returns.

If you need copies of old tax returns, see:

Need a Copy of Your Tax Return Information? (http://www.irs.gov/individuals/article/0,,id=110571,00.html)