Hello,
thanks for the query.
There are two possible and very important origins of your presentation that must be ruled out first before others; pulmonary and cardiac origins.
A possible pulmonary cause is Pleurisy which is fluid in the membranes surrounding the lungs. Pleurisy typically is accompanied with shortness of breath and could be associated with fever and mild dry cough.
Orthopnoea is defined as shortness of breath when lying down and it's a hall XXXXXXX of heart failure. However, at 35 years, this should be less likely unless you have conditions that could predispose such as secondary hypertension, thyroid problems, cardiomyopathies etc.
Other causes other than pulmonary and cardiac include: muscle spasm, inflammation of thoracic cartilages, and digestive causes. Fibromyalgia and muscle spasm would be less likely now since the symptoms occur only on the thorax and while resting. Digestive causes such as gas in the colon and peptic ulcers are also possible but less likely cause they will present with mostly unilateral pains.
Worth noting;
-If there is associated fever, pleurisy or chondrocostitis is more likely
-if there is underlying cardiac problem,( shortness of breath on effort, swelling of legs, palpitations, etc), orthopnoea is more likely
-If there is associated bloating, indigestion, exercebaton on consumption of fatty food, digestive causes are more likely
-if you have other associated muscle pain on your lower extremity with pains when you apply pressure on regions including your upper chest, inside regions of knees, upper part of shoulders, back of your head, outer parts of your elbows etc then fibryomyalgia is more likely.

Given the diversity of possible causes, a visit to a doctor is necessary for an in dept evaluation and tests such as an x-ray.

Hope this response would shed some light for us to progress better. Would be waiting for follow-up query if you do have any.
Best regards

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