If I import all my income from quickbooks self-employed, and then add my 1099s am I double reporting income?

Yes, if the 1099 MISC income is already included in your Quickbooks amounts.  If that is the case, you will want to adjust/reduce the Quickbooks income amount pulled into TurboTax for the 1099 MISC amounts you are entering for your business.

How can I adjust self-employed income after import, so 1099 MISC's aren't double reported?