tomtom - sad story, hope we can help.
Yes, there are ways to get your milk back. It may be a real challenge but with motivation you can increase your chances.
Expressing/feeding 3-4 hourly is not enough - it needs to be a minimum of 8 times in 24 hours including at least once at night, so yes, either wake him or express in the night.
Be careful with herbs. Some actually work against milk production, and you need to be aware of the way the herb is 'packaged' ie seed, oil, leaves some info here .
It would be safer to see a quallified herbalist, IMHO.
Work out a plan to reduce the formula. He may need formula for a while until your supply is built up, but if you keep the formula at the same level your breastfeeding will suffer - remember, frequent feeding/expressing drives the supply. Formula increases the gaps betwen breastfeeds and so works against the re-establishment of the supply.
Keep your baby close with lots of skin to skin contact and cuddles.
You can ask your doc about prescription meds to boost your supply, too.
Good luck.