Miscalculation on mortgage?

[Skylar Blades]

I'm newer to real estate investing as well as new to buying property.  The market I am in is very competitive and fairly high to get into. So the problem I am running into is the monthly payment on the mortgage being way higher than what I account for on the Rental calculator. I can't figure out why.

Basically the calculator say's that i should be in the green on cash flow with the mortgage and PMI but when i talked to my lender its roughly $500 higher than anticipated. Turning the unit into the negative with the going rent around here. Is there a work around that i am missing?

Any help understanding what I am missing would be greatly appreciated!