You tried to be not like your own mother,

 

you ended up like her because that was the only way you know how.  Dysfunctions run in a family from one generation to the next.

There is an empty hole in your heart, which should have been filled by your mother with her love and caring when you were little.  Needless to say, she didn't do it.

When you made efforts to attend to your son's every need (you should be commended for that,) you were acctually attempting to fill that hole, without much result, because it was your mother's job, and only she could have done it.

Every moment you encounter difficulties, that hole sucks off your energy because you feel the need to fill it.  Part of that burden also landed on your son's shoulders.  He feels the weight.  And he wants to break free.  Having a girlfriend provides that sanctuary.