I become aware of my breathing and feel like drowning

Recently I started to become aware of my own breathing. It happens when I don't have much to do or think so I'm sitting at home doing nothing, or at night when everyone is asleep and I'm alone. When it happens I start to feel like I'm not getting enough oxygen, so I force myself to breathe deeper, but somehow it makes it even worse. So I just breathe deeper and deeper, and it starts to feel like I'm drowning and I'm going to die, and my ribcage and chest muscles hurt because I'm trying so hard to expand my lungs as much as possible. I used to feel very panicked when it first started, but now I'm used to it and am actually pretty calm, but it's not helping.

I believe it's not a physical problem because it seems to be only happenning when I'm alone doing nothing, sad, or both. Also it gets better when I hold my breath or try to breath slower, so I don't think I'm actually drowning. I was on a solo trip which I thought cured it, because I never ever had a problem on my trip. But now I'm back to home and it started again. Is there anything I can do other than seeing a doctor?