How do I tell my Parents?

Ok I have had my first gf since 12/3/08 and I still haven't told my parents I have a gf. Valentine's Day is coming up and I want to buy her a gift and take her to the movies but I can't do that without telling my parents. I'm hoping that my friends will decide to go with their gf/bf in a group and I can tell my parent I going. If they ask if I am going to be like a third wheel I can just splurt out no I have a date too. But if not... Help me please. I keep telling myself I tell them the next time they ask if I have a gf, but then I get scared and say no. It's not about hurting my mother's feelings, its about the embarrment they give me. My mom saying' Awww, he's growing up." in that gushy way only a mother can. ANd my dad asking "Is she rich" and "Is she hot" or something of the sort. WHat do I do?