Since you have 3 weeks to do it I would eliminate one feeding every 2-3 days. As you do this your milk production will decrease. If you want to do it quickly I have heard to just stop nursing and wear the tightest sports bra you can or wrap an ace bandage around your breasts. I have never tried this way but have heard you still get full but that its goes away sooner then if you don't wrap them.
If you are in the US its a law that your boss gives you time to pump and a place that is comfortable and not the bathroom. Just heard about that rule when I stopped by WIC for info.
Flickan is right there are laws protecting breastfeading women to pump when needed and time to do so in a comfortable place besides a bathroom. You can Google the law for your state and take it to your manager.
Yep - by law your employer has to provide a spot for you to pump. If you decide to stop breast feeding before your return - I agree with the other post about dropping one feeding every few days. If/when you do get uncomfortable, pump to 'relieve pressure' not to empty out.
With that law they don't have to give you a private place to pump if it would cause undue hardship or if there are fewer then 50 employees. I had a friend fight with her employer over this when she was breast feeding. She was the only women working at a car parts store.
I live in australia so im not sure what the laws are here when it comes to breastfeeding. Thanks though will try reducing feeds every few days. :)