incomplete bowel movement

AGE 18 Yrs old male i'm able to pass about 70% of the stool but then I get to a point where I can feel the remainder inside my rectum but I just cannot push it out no matter how hard I try. My stool is semi formed alot of the time - I feel it has no real bulk. After being unable to empty completely in the morning I often feel gassy, bloated , unrelieved and end up needing to have a second bowel movement after my next meal (lunch). When I do go again I have a similar problem as I did in the morning where i'm only able to empty about 60-70%. I find if I push really hard after i've emptied that first 70%, small thin pieces will come out. Once again i'm left feeling gassy, bloated and not completely done. I may go a third time but the outcome is always the same as the first two times. As a result I pretty much never have a feeling of total relief from having to go to the toilet