I read somewhere that even if you eat junk, your breastmilk will still be good for your baby because your body will use the "stores" in your body to make the milk, eg calcium, etc. The only problem with eating junk is that your own health is going to suffer.
Why not opt for confinement catering? If you find it too expensive, you could even opt for normal tinkat meals, delivered to your door. At least you still get some meat and vege everyday.