I would be careful about exercise on LT with a four month old. You just won't have the same energy level as someone who hasn't had a baby recently.
Just looking after your little one and physically recovering from the birth and the hormonal upheaval, is enough to cope with for now.
You know what? The time goes by so quickly when they're that size, just relax and enjoy your lovely baby.
All the daily things you do will be enough and if you DO feel energetic one day, get the buggy out and go for a brisk walk and feed the ducks. Take good care of yourself. xxx