I contribute a little over 7000 a year to my TSP and the system says I'm over contributing to my traditional IRA. Am I selecting the wrong retirement plan?

Yes you are.

Your TSP account is funded directly through payroll, you do not report that on your tax return. 

The amount you contributed is already subtracted from your income (not in Box 1 on your W-2)

....i.e. you Do Not enter it as an IRA contribution.... IRA contributions are something you might do....but is done completely separately from your TSP.

A TSP is NOT an IRA.