well, first of all, there is usually always a medication that nursing moms CAN take. find a book called "medications and mothers milk" - a local la leche league group should have it, otherwise, try a library or amazon. you should be able to find someting to take that doesnt affect your nursing.
also, btw; breastfeeding IS beneficial at all ages. it gives immunity and milk specifically formulated by nature for the age of your kid.
other than that, also contact the local la leche league for tips on weaning. moms who are leaders of la leche league groups have nursed for one year or longer. so they will have real advice for you. my son self weaned at 20 months while we were on a trip. im wondering if the business of the holiday helped you and your son drop some nursing here or there.
dont ask dont refuse is a good method.
the other thing is to rearrange the furnature. put him to bed in a separate bed (nothing against co-sleeping or bedsharing - i love both! just to put him down in a different location to not "remind" him to nurse). just try to distract him during times that you would nurse. read a book, watch a movie, whatever. when you "graduate" from one form of attachment, you should always replace it with another form of attachment. this way your son is still bonded to you, and knows you arent rejecting him, but doesnt have to do it in the same way
ive heard moms using the "its broken" method too. just say "mommy's milk is broken" or something. after a few times, this might work.
either way, unfortunatly, its probably not going to be fast. its gonna take some time. though i havent seen if you updated this.
anyway. good luck!