Hi A., indeed, it is a little too early yet to offer cow's milk instead of formula or breast milk. Your son might not be interested, but that is his way of getting ready to switch to regular "big people" food. My daughter did the same thing--more interested in food for awhile, then she suddenly wanted to drink her formula again. It's sort of an evolutionary practice, babies bodies are very in-tune!
The reason it is too early for cow's milk is because there are carefully measured amounts of vitamins, minerals, and other "brain-building" proteins in baby formula. That is why ped's say first year breastmilk or formula ONLY. After that 12 month period, then begin offering it.
I understand about finances...not sure about your situation, but when my husband lost his job (I am a SAHM, too), we joined WIC downtown Frederick and they were WONDERFUL. We had all of our babies formula paid for for her first year of life. You can also ask your pediatrician for samples, or go on freecycle.org and sign up for the Frederick group and ask specifically for your child's brand of formula--there could be someone with extra to offer.
From the website of Dr. Sears:
The answer is that if you give an infant under a year cow's milk, the infant can develop microscopic gastrointestinal bleeding (you don't see it in the diaper), and this can lead to anemia and other problems. Yogurt does not cause this same reaction. Now: WHY does this happen? It seems to be the milk proteins that are responsible for this mild allergic reaction. In yogurt or infant formulas, the milk proteins are "de-natured" by heat in such a way that this allergic reaction does not happen.
Dr. Jim
http://www.askdrsears.com/faq/fit23.asp
I know you are a good mama, but you can always ask your baby's ped for more advice! Good luck!
N.