Are you sure he is really self weaning or is it one of the usual phases that kids go through where they reduce requests for a bit, then take back to it?? Is he still being nursed BEFORE he is fed his solids each meal? It is still considered more nutritional for him to nurse first, then use solids as a back up filler for kids up to at least 12 months... If he isn't being nursed and filled with breastmilk before his solids meal, then your milk will slowly decrease and he will be absorbing less nutrition too. If you are contemplating giving him formula or cows milk, then there is acknowlegdment that he still needs nutrition other than solid foods, so why wouldn't this continue to be breastmilk which is meant for a human baby? If you think your milk is decreasing it could also possibly be reduced by reduced nursing sessions (supply and demand!)ovulation, restart of your period, pregnancy, birth control, stress, etc. If you want to continue nursing and maintaining some milk, you could take fenugreek capsules (abvailable at any health food store), drink coconut milk (plain or in a drink), drink red raspberry leaf tea, eat oatmeal, and drink LOTS of water. -Also, don't be so quick to think that you don't have much milk just because you can't pump much out. That is VERY normal, as MANY women can only pump a small amount yet the baby nurses differently than a pump and can draw much much more out. Maybe you might want to talk to a lactation consultant for more professional advice? The one at Morton Plant is great and free. ###-###-####
Breastmilk is still very beneficial at this age and it is very rare for a baby to self wean before a year unless they are being offered other foods first and filling up....then they just lose interest, which also results in a decreased supply. Its a circle!
Personally, I would continue to nurse before each offering of solid food and I do not recommend cows milk. It is becoming more well known (even by pediatricians) that cows milk is not as good for people as once thought, and in fact has many negative factors to its constant consumption. Sure, once in a while -ie. on cereal or when baking won't be bad, but bottles or glasses of it daily aren't nutritionally necessary. Most people think of it's benefit being associated with the need for calcium...but calcium is needed in much lower levels in kids (especially an infant) and can be provided EASILY in their regular diet without the need for drinking cows milk. There is lots of good advice on the web about calcium rich foods :-)
There are many other good drinks, water being one of them, but if it were me I would increase your breastmilk supply (if it is really even low) and continue to provide the very best nutrition you can for your infant...breastmilk. Best wishes with everything :-)