Hey! I used to sing with a weak 'head' voice, till I suddenly 'changed gear' during a Strawhead concert.
I think that at school I was always expected to sing in a key much too high for my normal voice, and this came to seem normal. Only when I tried singing in a key much lower than this, with lowered inhibitions (couldn't hear myself think) allowed me to find a much lower, stronger voice. This meant that my husband Pete had to change all his harmonies, but hey!
We are singing with a couple of friends now, and have managed to get Carol to use her chest voice too, so she sings with a much stronger sound. I'm sure most women need to try singing much lower than most do. Try using the voice that you would use to communicate with someone across a large, windy courtyard! regards Jane Mickelborough