You might want to try banana and lots of water. I had the same issue before and it worked for me. I really don't know any scientific explanation about this method but this one was shared by a friend of mine who had OMAD.
Banana works very well, I can attest to that very well because I have used it on several occasions during my own constipation experiences.
Also try watermelon and oranges, they are both very good when it comes to helping you get your constipation crises taken care of.