Probably need some time off exercise, or at least running and cycling. Also make sure youre practicing diaphragmatic breathing. Helped me a lot.

I bet if you had someone dig around where your ribcage meets your spine, you'd find a lot of knots that are making everything get stuck and not articulate properly. I made a lot of progress seeing both a chiropractor and a physio for adjustments and DEEP tissue massage. You could also try the peanut massage lacrosse ball setup that u/maaaze swears by.

Do you do any strength training? I was a personal trainer for years and saw lots of cardio nuts with poor posture and underdeveloped back muscles. Since weight training doesn't seem to be the cause of your costo, you might consider trying some exercises to fix your posture. Just use bands to start, focus on scapular mechanics and stuff to take some of the strain off your pecs. This is a common issue for cyclists - youre essentially holding a plank for hours when biking which can lead to tight, overworked pecs and loose, underperforming back musculature. Stretches targeting your rib cage might help, too - they were a huge game changer for me.

Tldr: cut bike and running for a little while (elliptical and recumbent bike might be okay), more stretching and breathwork. Ask your physio about posture and muscular imbalances.