O- is relatively uncommon. Someone who is O- is a universal donor, which means that anyone can receive your blood. However, people who are O-, cannot receive any type other than O-.
It's actually very important for people who are O- to give as often as possible. In emergencies, O- may be given to a patient while they wait to get the blood typing done.
So, yes, your blood IS more needed than other types. Please give.