Did any one else doubt themselves when you found out you were pregnant?

I am 19 years old and I just found out I am pregnant, and I am kind of stressing out big time. I have a partner who is more excited than me, I know he's great with kids and he wants this so bad, but I am filled with doubts and fears like what if something goes wrong or is wrong with my baby, or am I too young to be a great mum, what if my partner leaves me, just a bunch of random things I wouldn't usually worry about. I just want everything to be perfect for any human I bring into this world and I'm not sure if I will step up to the mark, I still feel like I need looking after you know and now I have this whole person who is going to be the most precious thing to me in the whole world! Agh.  I haven't told anyone yet except my boyfriend but he has a terrible sleeping patterns and is still in bed, and I have just been thinking about the future all morning. If anyone has babies, how did you feel when you first found out? Did you doubt yourself? Do motherly instincts just kick in? Because I feel kinda lost - happy but lost.