Honestly...if you don't want constipation, change your diet.
Eliminate processed food, fried food, snacks, chips, soda etc.
All that and the lack of fresh vegetables is the cause of constipation and lumpy hard stool.
Instead of eating pringles, eat vegetables sticks when you're hungry. Buy a juicer and make fresh vegetable and fruit juice. Carrot, celery, brocolli, spinach, apple, cucumber, blueberries etc.
There are so many juicing recipes out there. In your case you may want the fiber to help your digestion
so a blender would be better. Blend blend blend! Put all the vegetables & fruits in the blender add some yogurt and ice...and you have a smoothie. If you'd rather chew your vegetables, eat a big bowl of salad everyday.