Four weeks straight of every workout completed and my abs groove is back

My body is definitely changing. And quickly. I was not feeling it for my workout today. And yet I dragged my ass in and did it anyway, plus I added weight and completed all of my reps. I've been feeling more sore and lower energy this week. I think maybe I'm not eating enough or something. When I make up my workout tomorrow, that'll make four weeks with all five workouts completed. After I was done I looked in the mirror in lower light as I went into the bathroom, and I noticed that that groove in the center of my abs was back. It was a lot more distinct, and it goes most of the way down. I felt, and sure enough, my gut is noticeably smaller. I still have a fair amount of slop at the very bottom, but that seems to be just where my body likes to store fat.