New move issues with breastfeeding

So my 3 month old son and I just moved 2000 miles across country. I was strictly breastfeeding but on the trip I had to supplement formula. It's been a couple weeks of trying to get things together and get my milk supply back so I am still supplementing some. He just doesn't seem to get full unless I give him formula. Even a pumped bottle of 5 or more oz isn't good enough. I'm not sure what to do about this and was wondering if I should just stick to formula now or try something else. I also don't know when I can start introducing cereal in the milk or any other types of baby food. Please help this first time single mom.