When I get up from a sitting position I become dizzy, when I walk a short distance I become short of breath, when sitting for long periods of time my lower legs swell, and I have been experiencing a hard to breath sensation when laying down flat to go to sleep.
Thanks for your question on Chat Doctor. I can understand your situation and problem. By your history and description, possibility of cardiac disease like congestive cardiac failure (CCF) is more. You are having breathlessness on exertion and orthopnea (breathing difficulty in lying down flat and in sleep). Both of these suggest CCF more. Dizziness suggests high blood pressure. So better to consult cardiologist and get done 1. Blood pressure monitoring. 2. ECG 3. 2d echo. You may need cardiac supportive Chat Doctor.  So better to first diagnose yourself and then start appropriate treatment. Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.