Question about BJJ and physique.

I have been a huge fan of MMA and BJJ for over a decade but only recently started training BJJ at a gym. I have my first tournament in March. I have been doing BJJ for about 4 months now and I have fallen in love. I train about 5 times a week (1-2 hours). I day dream about it and I can't see myself ever quitting. I only have time to dedicate myself to one type of physical activity. I have given up weight lifting and muay thai to focus on BJJ. Although I feel fantastic, I have noticed my physique is not looking as nice as it used to. I feel like I have lost muscle mass and feel generally softer around the mid-section. My 6-pack is barely a 4-pack now, which I don't understand considering how much more I am using my core in BJJ drills and rolling sessions. I have exerted myself in BJJ more than I can ever remember in any other activity, even throwing up on occasion after surviving the shark tank.

Even if you look at most BJJ guys they're typically not the most shredded or fit people. Even some high level BJJ guys sometimes look out of shape. For people who have been doing BJJ for some time, can you guys shed some light on why I am not building or sustaining any muscle while training BJJ? I feel like I'm working my muscles a lot and am generally sore for a few days after a hard session. Why is this not translating to an improved physique?