Thank you all so much for your ongoing support,
I used to be on 7lpm before(which was standard in my country) but now I'm on 10lpm.
Perhaps the outcome might be better with a higher flow around 15lpm, but I would listen to my doctor for now and stick with 10lpm as it's still producing positive effects and helping me ease the pain (I'm female and very small so maybe that's why).
And as CHfather pointed out, it was my supplier who picked up the tank size. Apologies for the miscommunication!
I'm able to keep a few tanks at home so the size is not a problem for me at this moment but again, thanks to you all for the helpful suggestions.