My DS had reflux, it was horrible as a FTM knowing something wasn’t right, but I was continually fobbed off with ‘babies cry’ and one GP even tried to suggest I was depressed. Anyway, long story short I saw my HV who agreed with me that DS had reflux and gave me the name of a private paediatric gastro consultant. He saw DS at about 10w old and diagnosed reflux. Put him on Neocate formula (as whether intolerant or not dairy exacerbates reflux) and omeprazole. He was like a different baby within days! Still sick, but pain free.
I really feel for you, it is bloody tough! So firstly i’d try the usual tips of raising head-end of cot (stick some books under the feet), keep upright for 20m or so after each feed. Try putting her in a sling for comfort and staying upright. My DS also liked a bouncy chair. Try feeding little but often to give tummy time to digest. If none of that is working see your HV or GP and ask for a referral to a paediatric gastro consultant. Or if you can afford it, go private. And if you are BF try cutting dairy out of your diet for a couple of weeks.
You can also buy something called carobel which thickens formula (and I think you can use with expressed bm). Check with HV/pharmacist before you use that but it did help with my DS.
Finally, and this is not for everyone, but we started putting DS on his tummy to sleep on my mum’s advice after weeks of me barely sleeping with him propped upright on my chest all night. So during the day he napped on his tummy in Moses basket while I watched him. Then we got an Angelcare movement monitor for night in his cot. That made a huge difference to how well he settled. But obviously it goes against current advice. He was over 10w when we started this and was able to wear a sleeping bag.
And most babies do grow out of this by the time they are walking. Sounds like forever away I know but it’s true. Good luck 