shay, if you did/do love your girlfriend then why cheat on her?..
and as for your age:/ at fourteen years of age you shouldn't of been thinking about 'birthday sex' you should of been thinking about what flavor birthday cake you was gonna get!.
anyway your girlfriend can't just blame you for getting her pregnant its also her own fault if she agreed to have sex with you, after the first time she didn't have to carry on having sex with you she could of easily said no, but then i can see where shes coming from at the age of fifteen no girl wants to find out there pregnant, her first reaction would be to blame you if you hadn't of asked for 'birthday sex' then she probably wouldn't of had sex with you that day and it probably wouldn't of carried on for the past year but anyway it takes two to tango.
if your saying she was fine with having sex with you and never said she didn't want to then your not just to blame and she needs to realise its just as much her fault then yours.
and so what is she 3 weeks pregnant now or more? and how long did she know she was pregnant before she told you?...
i rate you for saying you'll be with her for whatever she chooses because most boys your age would just run a mile and leave the girl...
as for her parents if shes saying she doesn't want to have an abortion then she will have too tell them shes pregnant how does she expect to stay pregnant and bring a child into the world without them knowing? she doesn't have to tell them at what age she had sex or anything she could even say that the time she got pregnant was her first time having sex maybe then they wont be as mad/disappointed when she tells them.
There is always the option of her going through with the pregnancy but then giving the child up for adoption at birth or even keeping the baby, but you'll both have to think hard about what choice to make.
a baby isn't a toy, it cant be past around it needs a stable mother and a stable father to bring it up so it can have the best possible life you've just got to think if you can give it that, im guessing your both still at school? if so how do you expect to get money for the child(it isn't cheap/easy having a baby.... trust me) how to you expect to get a good education if your life's focused on your child.
im 19 and i myself have a 1 year old son it wasn't easy and it still isn't moneys tight at the moment but i would never change my son for the world, having a child changes your life! sometimes for the bad but mostly for the good.
and i didn't know anything about pregnancy or babies either well not much anyway... its something you naturally pick up once the child's born.
hope this has helped:) you just need to think about your options properly!