I have been on Mycrogynon for over ten years (except for the year off it when I planned and had my baby lol), I never experienced the problem you describe until recently, and I wound up taking three packets without a break because I was worried about the protection I was getting.
Basically, I think it was my own fault in that I might have been a bit lax in taking the pills regularly, I take them everyday, just not always at the same time.
I would imagine it is more than possible that stress and the change in your diet could cause your periods to lose sync, and for the the pill to be less effective (hence getting the period).
Make sure you use extra protection, and take the next packet without a break. Most importantly, try and make sure you look after yourself - having the stress of an unwanted pregnancy sounds like it is the last thing you need! x