And your breast feeding too! Thats a hard job and takes a lot out of you.
My second son just turned 3 months yesterday, and we only managed to b/feed for 2 months. Im lucky to have a very easy baby this time, my first was was poorly with reflux and colic and it was hard on everything.
Even my doctor has said that the first year of having a baby is not a time to think of losing weight. Take it easy on yourself, sometimes you do just need a treat - its hard work!