I'm going to weigh in on bcd too small.
of course this is contingent upon how much actual weight you've gained, especially around your middle. How often do you dive in a year? I'm basing this on your breathing being fine at depth. As you know, we can often snug up the bcd again at depth which means it's not as tight at depth and therefore not squeezing on you like at the surface.
If on the other hand, you haven't gained any weight and have had no change in body proportions, I'll change my vote to anxiety. It makes no sense that's the weirdness of anxiety.
But overall importance is as others have said, go see a doctor for full testing.