LLL are lovely, and were a great support to me when (self)weaning ds1. he was of similar age as your ds (ds1 was 28 months old), and i remember very well those strong emotions when he finally stopped: i also had trouble remembering his last feed, and certainly didn't think whilst feeding him for the last time that that was it...
the single thing that made it easier for me was the fact that at the time i was also feeding ds2 (i tandemfed both of them for 4 months, which was a lovely experience). (also BTW, although it sounds like your ds is ready to self-wean, i hope you know that wanting to conceive again doesn't need to be a reason to stop feeding your firstborn...)
anyway, because i was also feeding ds2, i didn't need to cope with full aching breasts. also, it was sort of a relief for me to know that there would still be milk, incase ds1 would get sick, and would need the comfort of a feed.... i thougth like ou, taht there would be no other way, or no better way to comfort him than a feed... but there is: as tiredandgrumpy already said, cuddles from mummy will provide them with comfort as well, and this is what my ds1 woudl do, take the position to have a feed, but then have a big hug in stead.
now, almost 2 years later, reading your post made me realise how much i should treasure the fact that ds2 (2y1mo) is still feeding! and how close i could be to him self-weaning. i was close to tears, and cuddled ds2 a little bit extra this evening after his nightime feed.
it will get easier, i am sure, just be prepared for those nasty hormones to wreck havock for a little while ...
but be proud of yourself: you have given your child the best start in life!