2D gaussian fit with cross correlation

Hi, I have an image with a point source and I am trying to find a best fit 2D gaussian curve. I generated a matrix with a bunch of gaussians with different spreads and used cross correlation function to match each of these curves with my original image. The code works without throwing errors, but the result is wrong. To ensure my code works, I generated a gaussian of width 20 and used the code to measure, the result was 15. Where am I going wrong? Thanks in advance for your help!