Your symptoms can be caused by many reasons. It could be anything from a simple heart burn or acid reflux to some herat related issue. It is impossible to say without a detailed history and examination. If the pain and tiredness is increasing, consult your nearest physician.
Next Steps
Consult a physician.
Health Tips
If the main problem that is bothering you is difficulty in sleeping upright, then try sleeping with the head end of the bed raised, perhaps with a couple of pillows behind your back. Take care that your entire upper torso is raised and not just head and neck. Wait atleast 2 hours after dinner to go to bed. Do not drink too much water right before sleeping. Avoid acidic foods like curd, lime etc