Hi Kristie,
From memory, Gabby also had a bit of a change when she was around 4 months. I think it was for my 4 month check-up at the MCHN that I was told she hadn't put on "enough" weight and that my milk supply must be low. I was encouraged to give her more formula etc. etc. As it turns out, it was probably just a normal 4 month thing for her to have not had such a huge weight gain (and no need for the MCHN to put low supply issues into my head yet again!).
I think her sleeping habits also changed and we had a couple of off nights.

I really don't think you can attribute what is happening to Louis to any one thing. Give it a week or so and it will probably sort itself out. You are obviously feeding him enough and making sure he is warm enough so he's probably just having a major growth spurt. The frustrating thing when these sort of things happen is that you don't really know what's going on until after it's all over! LOL Kind of like teething symptoms. Often we don't know what's happening until after the toothy-peg pops up!