When should I seek attention?

On July 13th I had diarrhea. Since then I haven't had a bowel movement. Ever couple days after sitting there for a half hour I'll go a little but hardly any. I eat raisin bran daily and since the incident I started taking psyllium husk tablets daily. I drink around 5 cups of water a day. Coffee hasn't moved my bowels either. For the last 3 days I've gotten really nauseous. Today I drank about 12 oz of prune juice and it only made me fart. I don't have cramps but I'm really starting to get worried. When should I see a doctor?