Constipation Woes. Should I see a doctor?

Okay, do about a week ago (say wednesday), I noticed that I had diarrhea. I was going to the washroom like 5 times in one day and everything was all watery. So I took some Pepto-Bismol and the diarrhea went away, but now I'm really constipated; it started on saturday and it's now monday and I'm not getting much relief. I've been eating tons of foods that help in this sort of situation (plums, products high in fibre, probiotics) and drinking lots of water. And just yesterday I started taking senna pills to help it along, but nothing is really happening. Should I go see a doctor?