I have read a few people talk about having trouble with constipation. It is not fun. I know.
Senna tea works great. It can be a little harsh even. At my store these teas are back by the pharmacy and can be called "smooth move" or "digestive" - read the ingredients. If there is senna listed, that's it. Drinking a full cup can be somewhat harsh. I have a 4 c. coffee press and this last time I put two senna and two green tea bags in it. I drink one cup of that a day and no worries.
My health food store sells just senna tea so that's another source. All I can say is, "It works".