First of all, way to go! :) Pumping can be a huge pain... I pump 3-4 times a day because I work full-time and my son is 7 1/2 months old now (have worked since he was 10 weeks).
I have a cousin who exclusively pumped for her twins for a year plus worked 3 days a week. Basically, you have to decide how important it is to you and your baby. Your baby will develop just fine if you quit and feed her formula... but you have to really be OK with that.
I have had many times in the last few months when I was overwhelmed by things and thought quitting breastfeeding/pumping would relieve some stress... but when I really think about it (when I'm NOT as stressed out) I'd really miss it and be dissapointed in myself if I stopped for those reasons.
If pumping is really the root of stress and anxiety for you, then that would be something else entirely. I just try to think ahead a few months and decide if I'd be happy with that decision in the long term (and have so far always talked myself out of quitting, for now). You are doing a great job, take care!