It's likely muscle, especially if you're working out regularly and eating healthy. On T, you will gain muscle MUCH faster than it would have ever been possible before, so definitely take advantage of that and keep it up!
Also, weight doesn't redistribute on its own. It will happen over time. You have to first lose the existing fat (T makes it easier to lose fat from female places), then when you gain new fat, it will be much more likely to stick to more masculine parts of your body. Unfortunately, a lot of people seem to be misinformed and believe that it all just happens on its own. That's how you end up with guys who don't work out and wonder why they've still got birthing hips 2 years into T.