Yes it could be. Most of the time it is not really that noticeable to look at, but you can feel that you have because you might not feel as uncomfortable under the ribs, and like you say, you need to go to the toilet a lot more. It's all to do with the baby engaging and moving further down into the pelvis, which can make your belly look lower or different.

I only ever 'dropped' with my second baby, and I think it was because she was the shortest of the three and she didn't take up as much room IYKWIM?