Looking for advice

Kind of a gross subject but I just can't get or give answers. My boyfriend has been having constipation problems for about the lst 5 months. He says its' painful when he tries and sits there for about 20-30 minutes. He also says he feels the need to go but then can't. Our dog just had the same problem and I switched her food and now she's fine. Do I really have to quit giving my boyfriend kibbles and bits too

Lol, but really we eat very healthy. All the right amounts of fiber, pastas with added fiber, lots of milk, pretty much what guys normally eat. And a lot of it! Does anyone recommend anything else??? I've heard of the stool softener, fibersure, ect. has anyone used it??? I was also thinking about a cleanse, or detoxifier. Please help!