Supply not responding to cluster feeds?

I've got a call into the LC but figured I'd give you ladies a "ring" while I was waiting for them to call back. I'm about at the end of my rope after DD has been seemingly having her 6 week growth spurt for the past two weeks. I don't know how long the more frequent feedings are supposed to last to build up my supply but two weeks seems too long - and feels too long for my tender nipples and sleep deprived mind. Plus it seems to be getting worse as she was still going a good 3 to 3.5 hours between feeds at night but last night went no longer than 2 hours. She's been feeding every 2 hours during the day for the past 2 weeks. The last 24 hours have been especially exhausting and overwhelming.

This afternoon I decided to give her a bottle of BM to know that she was getting a good amount (4 oz) and we're just a few minutes from 3 hours since the bottle. This makes me wonder if she's not getting enough from me. I make sure to let her stay on as long as she wants and offer both sides. She's maintaining the same number of wet and poopy diapers which the LC (who just called back...) said indicates that she is getting enough but I'm just so burnt out with the frequent feedings. It doesn't seem right to me that she's not yet back to going longer between. Two weeks of this is like forever in the life of an almost 7 week old!