Irregular bowel movement and difficulty going.

I have had problems with constipation since I had my second child 15 years ago. Lately it has got to the point where I don't even seem to get any warning signs and seem o go days at a time without going. When I do go the stools can be small and round or large and dense and seem to get stuck to the right of my anal opening. I don't seem to be able to push or have any sensation of pushing. I eat a very healthy diet encorporating fruit, veg and cereals. I always seem to feel thirsty, sometimes the more water I drink the thirstier I feel.. I feel sluggish and bloated a lot of the time and lethargic. I don't want to become reliant on laxatives and am fed up of been told that there is nothing wrong. I am 47 years old. Can anyone shine some light on this problem as the worry and discomfort have now overthrown the embarrasment I feel havng to highlight this problem on the site. thank you.