Im betting 99%of people say a similar thing. Ive always been fairly fit but when my emma arrived and i had to carry her up a flight of stairs i did wonder what the hell id got myself into. 2 years later and with 4 girls to look after I still make the old man noises when i pick them up although it does get a little easier as time goes. You learn ways to carry them and your strength will improve.
Best of luck and welcome to the forum.
Have a good long gaze in her eyes and she will tell you her name, you'll soon forgive her for the weight