at this age, and at this time in your bfing relationship you may not be as sensitive to the pump.
It is most probably the 4 mth GS. I found it the worst of all of them, both times!
For me, I hated waiting for the GS to end and loved to find "something to do" to fix it quicker -and as my two were already STTN consistenly from 3 mths and earlier even, I wasn't willing to go back to sleepless nights for me and them.
My daughter also had an unclipped yet diagnosed tongue tie at this moment (was clipped just shy of 5 mths) so she was hopelessly distracted and not at all able to deal with GSs alone, without the help of the pump.
When I saw tiny signs of the GS coming - hungry after 2/2.5 hrs etc....and tetchiness or NWing....I just started pumping on empty at the end of every feed, all day, every day, for around 3 or 4 days. Whatever I managed to pump -day 1 probably a couple of oz for the whole day, day 2 around an oz after each feed, day 3 2 oz and so on, I used to top off the most important feed first (for us it was the 7pm feed as it was the most distracted or OTd) and later when I had an oz or two after every feed, I used the milk after every feed.
By day 5, we were back to breast only and I had signs of fullness in breast, engorgement etc.
If you do use this method, don't be put off by pumping and getting nothing out. It really took a day of 15 mins pumping each side after each feed with nothing at all coming out before I was able to get an oz or so each pumping the second day....
This was the worst GS as they need much more at this age and can't get have solids....and I was used to, or getting used to, STTN as well ;-)
After this, I never really noticed GSs in terms of bfeeding as for the 6 mth spurt we were on solids....
S x