Im confused. Dd is 4mo and when we stay home she will be awake for 45 minutes playing nicely and happily and then starts to fuss and get upset and nothing I do seems to get her really happy again whether we try an different activity or have a bit of quiet time or have a feed etc BUT if I then take her out in the sling she is happy as anything chatting and smiling away for about another hour and a half before falling asleep in the sling. I don't understand why she seems to change at the 45 minute mark and why she can then be so happy in the sling. I don't mind having her in the sling but it would be nice to be able to stay in the house and play without having to go out. Any advice please. Thank you.