AT this age breastmilk is still the #1 source of nutrition. From age 6 mo to 1 year solids are supposed to be merely for introduction to foods, textures, tastes, social table experiences, etc. Even what they do eat is barely absorbed and processed to gain much nutrition. That is why your Dr is telling you to wait. As much fun as it is for parents to experiment and try new things with our little ones, sometimes it is not best. Their gut is not ready and like the Dr said, it can cause allergies and sensitivities of the gut due to early exposure to things their linings have not matured enough to handle.
As for reducing breastfeed sessions...this is not recommended. Until a year, you should still nurse first, THEN follow it with a solid food offering a few times a day. The breastmilk shold always come before the solids so they get all their needed nutrition first, then just experiment with the solids.... It is not true that he should stretch out daytime feedings at only 6 months just because he can go 12 hrs overnight. He is probably sleeping all night due to taking in enough breastmilk by day.... if you start taking away his most important meals, you are probably going to end up with a baby waking at night to be fed the nutrition that he missed in the day. Count your blessings that you have 12 hrs at night and feed him whatever he requests by day! Every kid is different, follow his lead and answer his food requests. He may go months with this pattern and then Poof! he may have new, different needs on an entirely different day/night schedule. Go with his flow....:-)
Have you tried taking the full dosage of Fenugreek (3 capsules, 3x a day)? How about drinking Red Raspberry Leaf tea (from health food store) or coconut milk? If all else fails there is a presription for increasing supply to avoid feeding formula. You can also buy breastmilk from a milk bank to avoid formula as well... Pump more often to tell yor body you need more milk....Always pump immediatley after the first two morning feeds for sure, when milk is in highest supply. You should be producing more and saving more in no time with all of these tricks!
Last - the best recommended first foods at 6 months I learned at LLL meetings are avacado, sweet potato and banana.