Blimey, once it has sunk in properly , it will be fantastic, I have a 13 mths gap, and we were ttc for 3 mths before I fell again - it will be fine.
Your kids will be so close in age, be easier for activities later on, rather than two different age groups!! Plus at least with your daughter born in Feb , your new baby will be oldest for their year at school just catching the next year intake I believe , if your first had been born at a different time of year, you may have had them both in the same school year , with a larger disadvantage for number 2.
Congratulations , wishing you a happy pregnancy