I'm a single mom and I gave my babies my last name every time. If their father and I get married, I'll just change their last names in court - no big deal. But I'll tell you, it has been easier on everyone with their last names being the same as mine. He can argue with you all he wants, but when it comes down to it, it's ultimately your decision. But think of it this way, when people make something or discover something (a new planet in space, build big buildings, a new invention or a new medicine or disease) they usually name the new "thing" after the person who founded/created it. You carried your baby for 9 months - you created the baby, I would name it after yourself if I were in your shoes!
Also, if you really wanted you could give the baby his last name, you don't have to be married to give the baby his last name. You can name the baby Elvis Prestly and the hospital won't care. Legality doesn't come in until it's time to sign the birth certificate. IF you're not married he doesn't have to sign it - but if he does, he's automatically considered the biological father and could be responsible for child support, etc. even if he disputes paternity later on.
Just giving you a run down - I've been a single mom for 10 years now - my youngest is 2.