Firstly, you are doing a fantastic job and it shows that you want the best for your baby.
Make sure you are drinking at least 2 litres of water a day, eating well and make sure you are somewhere you are both relaxed and comfortable. Until about 6 weeks I remember cluster feeding was hard but ended up getting all my supplies at hand (snacks, water, my phone, remotes, muslins, etc) and going through box sets.
Formula top ups are a trap when it comes to breastfeeding, the more you up the supplements the less you make but you can reduce them if you only give a small amount now. Kellymom.com has great information on it and breastfeeding so does the UK Breastfeeding Support Facebook page (my go-to for advice!) - I wouldn't have made it to 9 months without that online support.
Babies have so many growth spurts around this age that they can fuss a lot and it feels stressful and like you're not doing enough. I remember breaking down over it and at 9 months we have had growth spurts recently too which felt very similar. Engorgement and leaking boobs are a sign of confused boobs at your baby's age so the fact that isn't happening is good, it means your supply has settled down, not that it has stopped or not come in (unless you have been formula feeding a lot, in which case it is possible your supply has dropped). Supply is also not indicated by how much you can pump either (I can't get much out unless I'm engorged and have gone a long time without baby feeding).
I'd recommend a lactation consultant if you can afford it, an IBCLC one. Mine was about £200 for consultation, cranial osteopathy and a tongue tie division as my baby wasn't putting on weight well and it turned out to be a posterior tongue tie. They will assess latch, positioning, can check for tongue tie but also go through a check list. However as mentioned it may just be a growth spurt. Was it better in between at all?
How is weight gain?
Do you mean your baby is being sick with formula or both formula and breastfeeds?