All I can say is, don't buy into any negativity and don't be scared to tell judgemental people where to get off. You know, the people who are looking at you and trying to figure out just how young you are and they are practically shaking their heads at you. They are rude and should be told that they are being rude.
My SIL was 16 when she fell pregnant and 17 when she had her first. He was the best thing that happened to her life because she stayed with the father and had a second, and 9 years later had a third! She told me about her stories of being made to feel like scum by rude people who thought it was their place to put her down and let her know what they thought of her...as if it actually matters what they think. I have another friend who was in exactly the same situation, too.
You are doing something that lots of other women couldn't do at an older age...and that is to take responsibility and go through with a pregnancy, so good for you that you can do this.
I hope you don't cop any attitude off people, but if you do, please tell them where to get off!
Have fun with the other younger mummies on BB