Domperidone is occasionally used but very much as a last resort. It would be a good idea to identify the lead infant feeding midwife in your trust and ensure than you are referred to her, perhaps even antenatally to chat about plans.
Good information about domperidone here www.breastfeedingnetwork.org.uk/wp-content/dibm/BfN%20statement%20on%20domperidone%20as%20a%20galactogogue.pdf
If you don't think you ever produced mature milk at all then I would suggest, given the history, that you express right from the start as well as feeding. Hand expressing at first for around 10 mins after each feed (and of course you can collect what you get and give it if necessary to your baby) and if/when you are getting good volumes of around 5ml per session use a breast pump.
I would suggest using a cycle on the pump to initiate lactation. Many electric pumps have this built in. If you have one where you adjust the settings yourself then this would be using high cycles (how frequently it sucks) and low vacuum (how string it sucks). Decreasing the cycles and increasing the vacuum to comfort level if/when you get a milk flow.
However, you need to balance this with your mental health/sanity/family life etc. A regime like this is very, very draining for you.
When expressing like this give yourself a break of 5 hours once in every 24. Use it when it will give you the greatest benefit. For you it might be to spend time with your other children, or it might be for sleep. Though do make sure you express at least once in the early hours of the morning when circulating prolactin levels are highest.
The most important thing is to enjoy your baby. Give it all you have but mostly enjoy it. You can't help the past, the PCOS, the breast development. None of that can be changed. That you have given your children any breastmilk at all is amazing and has helped them to have stronger immune systems and the best start in life.
It is great that you have had breast changes in pregnancy. Will you be having a section again? Make sure you talk to the midwife caring for you about skin to skin in theatre or if not possible in theatre because you are not well enough then in recovery. The earlier you have that skin to skin the earlier those hormones get to work.
I wish you the best of luck on the road ahead.