I think what needs to be addressed more than your little binge is your perspective on weight gain in pregnancy.
At the end of an average healthy pregnancy that goes to full term -
The baby will weigh 3-4 kgs
The amniotic fluid - 1 litre approximately
The placenta - 3/4 of a kg approx
Increased uterine muscles - 3/4 kg approx
Fluids and blood generated by the body to sustain the pregnancy - 2-3 litres
Fat deposits laid down to produce breast milk - 2-3 kgs.
So you are looking at 10-12 kgs for a person who enters pregnancy at an average BMI and eats nutritious, healthy, balanced meals throughout. Gaining far too less than that may not necessarily be the best.
I am not sure what you would have to sound vain about, or what you mean by staying on top of your weight, because this is one time of our lives whe our body creates a human being, an entire new organ to feed that human being and litres of fluids and blood and fat to support that human being. This translates Into weight gain.
Your macD meal and the choc bars aren't a problem, trust me. I am not very sure what you mean by eating light - if it's light, non spicy food you mean that's great, that will spare you heartburn. But if by light you mean a lighter amount of food, you may wish to check with your midwife.