For a start, @skyandmoon, you're not ugly. I used to have similar thoughts about myself, in my younger days, but as I grew older I noticed that people I had thought (commercially)'beautiful' in my youth had not weathered well. I learnt that beauty is fleeting, is skin deep, and is in the eye of the beholder. Someone (a man) once said to me that 'beautiful' people usually have shallow personalities. I, also, usually found it to be so.
I am sorry that you were left by your mother when you were four. That's very sad and clearly hurts you deeply. People are all carrying emotional, psychological loads of different kinds, some we inherit and some are inflicted on us, and we don't always understand people other than superficially. We are complex and so much of us is unknown to others. I don't know your particular situation and can't advise. I can only say that I hope that you find peace with it, and perhaps, find a way to rekindle your relationship at some time. Likely, neither of you are ever far from the other's mind, and both hurt deeply. Things are seldom as they seem and are usually much more complicated.
I cannot imagine why your mother left you. She had her reasons and I'm sure it wasn't because she didn't love you. I am sorry for your pain, @skyandmoon.
There just doesn't seem to be such a thing as a perfect family.