I had my daughter at 15 and now I am married with three children and both my husband and I have degrees and and nice home. We still look young and we still get bad looks and bad comments. The truth is,until you can ignore those people, being a parent is going to be that much harder. Anyone who is different from the norm needs to realize this in order to live a full life. Focus your energy on your child and your girlfriend.
I would also like to say that it is so great that you are an involved father. I graduated from a teen parenting program with thirty other moms and not one of the fathers of their children were involved. You are not the norm and you made the good choice not to be part of that norm. Be proud of it. You have the oppurtunity to be the most important man in your child's life. That is such a blessing.
Congratulations on your new family and good luck with everything.