strugglin any advice out there?

Roxie is still bf at 6 weeks old which is great but the last few days i think she having a growth spurt or somthing? she is feeding all day long constantly and im empty im sure as she screams after latching on shes not letting my supply build up at all and is not sarisfied after any attempt. i have given in and given herformula for a feed she has drank 2oz and screamed so is now got some more. i know im supposed to let her feed off me all the time to build my supply but she is screaming with hunger! i have my 2 year old to look after and run around after. im really struggling as she wont be put down arrgghh! has anyone else had this and did it pass? cant carryon like this i darent leave the house and dont like using formuka but i cant express any as she has drank it all!!!!!!! help x