My mom was 22 and unmarried when she had me, and I managed to turn out OK ;)
I waited till I was 30 to have my first, because it took me a long time to meet the right guy (and because I was SO not ready to be a mom in my early 20s!), but I have nothing but respect for young mothers. I mean, it's not as if you're taking the easy way out of this ... you had your baby and are loving her and caring for her! You could have had an abortion and not had to deal with nosy old women following you around and tut-tutting.
Btw, I do agree with the other ladies ... PLEASE, PLEASE, PLEASE try to stop smoking, for your beautiful little girl's sake. My mom is now 55 years old and smokes a pack a day -- has since she was 17. Neither she nor my dad have ANY desire to stop smoking, and it kills me. My mom told me once she probably wouldn't quit even if she got lung cancer, and it breaks my heart that cigarettes are more important to her than me and my sons are :(