Hi April M
Welcome and congratulations on your baby girl! You may just have what they call the baby blues, I had them after I had my daughter 17.5 years ago, I was just 18 yrs old and had no idea what I was doing, and to make it worse I broke up with her dad just 2 weeks before she was born. It may feel hard know but trust me it will get easier I proimse. If you start feeling really low, go and see your doctor, if you have a good doctor then they won't mind you going and explaining how you feel to them. there may even be a mother and baby group you could both go to and talk to other new mums that may be feeling the same as you.
What ever you do don't wish for your baby to grow up to quick, as once they get to the teenage years you may wish they were small again. Make the most of your time with her and enjoy it, they grow up to quick x
Hope this helps
Good luck with motherhood
Lee xx