Turbotax is saying I over contributed to my roth ira due to my MAGI. But my MAGI is under the $153000 limit, so why is it saying I can't contribute the full $6500 amount?

If you file single or Head of Household, you have a reduced limit if your MAGI is between $138,000 and 153,000.

The full amount is allowed only for MAGI up to $135,000.

See this IRS document.

From reading the helps on that page when I went through it, unless you truly contributed to a normal roth ira, not a 401k or otherwise, see if your contributions is excluded from that section and you can check 'NO'. 

Remember it's a computer program, sometimes you need to check 'no' if the end result of that section does not apply. In this case, the point of checking 'yes' is to ensure your contributions are below $6500.