You could see a trichologist for the best advice. Check out the Philip Kingsley clinics, they have a website.
If it's female pattern balding, then you could start applying Regaine, it really works, but you must continue it daily for the rest of your life to maintain the new hair, so you need to be prepared for that.
It could be temporary alopecia. It could be hormonal. Try not to worry, it can be prevented.