Unless you're all together unfortunate looking - which is very RARE - everyone can be extremely attractive just by doing what other posters have mentioned:
1. love yourself
2. decide that you ARE beautiful
3. live your life with passion and laugh a lot
4. take good care of yourself - grooming, dress, etc
As for some guys having extreme dislike vs showering with compliments, if you are also intelligent and beautiful, some guys see that as a threat. If you are working with guys like that, some of them embrace it, some of them have a total extreme dislike for it. So consider it a compliment. How they act towards you tells you more about them and very little about you.
Most guys are attracted to passion - a woman who has passion for whatever it is she has passion for. You can be "ordinary" but if you have passion, it is extremely attractive.
I grew up like you, plain jane, overly critical mother. When I hit my 20's (and puberty, yes, I was a late bloomer) I moved out of my mother's house. It was like a total 180. And I don't even ask myself if I am beautiful any more. I know the answer, and it has nothing to do with how I look. You are beautiful when you see the beauty in you.