can you try some grounding or distract yourself to get your mind off the tightness? also, most of the time difficulty breathing is bc you aren't breathing out long enough and have too much CO2 left in your lungs- try breathing in for 3 seconds, and out for 5

Try listening to asmr :)

This could be a lot of things but personally when I faced tightness it was related to acid reflux. This could be related to the chocolate. For a quick fix I would try pepto or an equivalent.