I would advice u to keep the baby. if ur dad can support u in this then go for it. Just think that if u give ur baby for the rest of ur life u will think about him or her and wonder how the life would have been if u kept the baby. Looking after a baby on ur own is not easy, but r u ready to leave someone who lived for 9 months under ur heart and never see him again?
U need to think in a long term. Now u probably think u r too young to cope with a baby. But how would u feel after years? Wouldnt u regret giving ur baby?
Also i am for taking the responsibility for our actions. If u were enough mature to have sex then u must be enough mature to take the responsibility which came as a result of it. My advice is to keep the baby and i hope ur mom after some time will fall in love with ur baby and forget her ideas of adoption.
Keep in mind that this baby will be her grand daughter or grandson. Sometimes parents over react out of shock in such situations but then when they see the baby their hearts cannot resist loving it.
So at least wait for some time after the delivery to see how u will feel about the baby and how ur mom will feel after she gets to see the baby.
Also 14 is not that bad as age. Ur baby will have a young mom when it grows up