In my left side near stomach i feel some kind of pressure everytime when i sit, walk and sleep but no pain only pressure and uncomfortable feeling.?

Doctor can evaluate: Sounds like there is something there. So, a primary care doctor can investigate. It could be in the abdominal wall, maybe some sort of hernia or some tightening of something attached in that area. It could be a tumor of some kind (the stomach, intestines, and pancreas are in that area). It could be a very large spleen, or a kidney mass, as anything large inside would be pushing on everything else.

Need to examine: It is not feasible to provide a meaningful opinion without additional history, physical examination and may be some tests. Your symptoms are suggestive of an enlarged spleen and you should consult a doctor as it is likely due to a treatable issue.