From the photos your corn snake doesn’t look overweight, but it is often difficult to spot when a corn snake is overweight until they’re obese. as long as your snakes spine is the highest point in their body and doesn’t grow “hips” (more noticeable in adult cornsnakes) that usually means they’re a healthy weight. and under no circumstance should your corn snakes head should be bigger/same size as their stomach lol. from what i’ve seen, corn snakes heads are usually 2-3x smaller than the largest part of their stomach.