Babies do have periods of time during which they eat/drink less. However, I wonder if all the moving and changing his formula around has upset his digestive system. Babies like routine and having the same flavor of formula every time.
My daughter was on WIC with her first baby. She had an appointment every month with a specialist who weighed the baby, talked with my daughter, and increased the amount of formula to the amount that she needed. You should not have to supplement with formula that you purchase. If the brand that they gave you isn't working they will switch to a different brand. Work with your WIC counselor so that you have a consistent and sufficient supply of formula.
Are you heating his bottles? Are you using the same style of nipple? Are you holding him while he drinks? Are you relaxed when you're feeding him? Are you in a quiet and calm room, with perhaps soothing music playing, when you feed him. All of these can affect how much he eats.
If giving him the same formula over at least a week's time, while cuddling with him in a quiet environment, doesn't work, then I suggest that you have him tested for allergies. His body could very well have developed an allergy to milk protein or some other ingredient in the formulas. This is another reason to stay with just one brand and one style.
Please immediately get involved with WIC in your new location. WIC is an excellent program that wants you to have enough of the right formula. The reason for their existence is to be sure that babies and children, along with their mother have good nutrition. What you're doing now is not working. Call WIC and find out their hours and when is the best time for you to go in.
Megan, I just read your So What Happened. Your wish to have him drink less formula is a big part of the problem. This is not good! Formula is his primary source of nutrition at this age. CALL WIC! They will give you enough formula so that you are not having to buy more.
You do have reason to worry. This is not a good situation for your baby. He is not eating enough. Even if he isn't losing weight he's not getting enough nutrition for brain and muscle development. You really do need to take him to the WIC counselor as often as they want you to do so. Having to move does make making and keeping appointments difficult but it's essential that you go to WIC and get enough formula to last. :You do not need to buy any formula!!!!!!