Hi Melissa, this can be tough. I have a five year old boy and one that's 4 1/2 months. I nursed my older son for 2 1/2 years and he was taking substantial solids by the end of his first year, but we never really used prepared baby food. Here is my advice.
Try giving him some more interesting foods that are solid but can be gummed into submission by your little boy (since baby's don't have molars yet, they don't really use their teeth for chewing anyways, so no teeth doesn't mean he's not ready for finger foods). My suggestions are small pieces of dry toast (peanut butter can be added when he's two, but no nuts before then, they're very allergenic), real banana slices, plain cheerios, quartered green grapes (seedless of course), soft cooked carrot slices, canned green beans (they're soft enough, but remove the seeds), small cubes or slices of mild cheese (added benefit of cleaning the mouth, naturally antibacterial), soft scrambled egg and gerber graduate meat sticks (they're very soft and manageable). He may not have teeth but all of these foods can be handled without teeth especially by a drooly baby. :) The cheese, egg and meat have extra protein that he's going to need and the fruits, veggies and grains are also necessary. I also gave my son diluted (1/2 juice, 1/2 water) white grape juice from the time he was 5 months on for another way to work in a serving of fruit. They love it and the sugars in white grape juice are more easily digested than apple and won't cause stomach discomfort. Of course with all of these finger foods, the trick is to provide only a little at a time and closely supervise him until you're sure he's got the mechanics of eating down and isn't at risk of choking on any of his food. Usually the first month or two. You'll know when he's got the hang of it.
As to your question about nutrition, a baby's primary form of nutrition in the first year of life is breastmilk or formula. Actually babies in highly allergenic families are routinely sustained on little else until after their first birthday and remain perfectly healthy. Please don't worry that your baby isn't getting adequate nutrition, he's getting everything he needs from your milk. However if you are trying to wean him he does need to be starting on finger foods like I mentioned above and after his first birthday he should start taking whole fat cows milk too. Doctor's recommend whole fat milk until they're two.
I hope this helps. You sounds like a great mom..keep up the good work.