Nadia I have endometriosis. Well not at the moment.
The best meds would be continuous birth control pill or other meds to prevent your cycle and bleeds as this is why the endo is active.
The problem with this is that you can't use it when wanting to fall pregnant.
I suggest you seek a very good fertility specialist even if you don't want more kids. I saw Dr Siebert at Aevitas in Pinelands and he did an extensive surgery where he cut as much of the endo out as he could. There may still be the odd patch here or there and I am not on birth control and so far so good. Cutting it out is certainly the best option for advanced endo with adhesions.
Sorry can't give info on pcos but again the fertility specialist will be able to work out a proper plan of action for you.
Good luck.