.net - Optimization With Visual Studio Or A Logic Bug?

I have an small physics toy application I am developing. It works fine except the particles will not push each other away, only pull towards, I debugged that sub going through it command by command and realised the value 'H' would not change, what ever it was set to during the first pass through the sub is what it kept, the only way to change this value is to manually set it i.e 'h = 1'. Once the calculation is redone on the 'H' value it resets to what it was previously, even though the x1,y1,x2,y2 are all different, thus meaning H should be different.

I think it is me that has made a mathematical mistake somewhere, but I cannot see where it is. I need a fresh pair of eyes to look over my work. Please let me know if you find anything.

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