First off, Welcome to the Healing Well Family - you have come to a great place to gain advice, insight, friends, and most importanly, support.
Simply put, yes, anxiety/stress can and do cause diarrhea. I have gone through a similar situation as yours regarding a relationship breaking apart and I had the worst diarrhea ever. I could barely get through a meal without having to run to the bathroom and this went on for what seemed like an eternity.
I am not a medical professional in any way at all, but I think this is what I would do - buy Pepto-Bismol, Immodium AD, or Kaopectate. Use it for a day or two, see what happens. See if it will help either slow things down or stop it all together. In the meantime, make sure to drink plenty of liquids (but stay away from milk, that will make it worse/continue) so that you don't become dehydrated. That's the last thing you need to deal with. Just within the last month I had diarrhea pretty bad for about two weeks before I called my doc. When I called my doc, she told me to start drinking Gatorade or Powerade. This will help to put the electrolytes back into your system that you are currently losing. I'm not a fan of the stuff, but it works. My diarrhea ended up being from one of the meds that I was recently taken off of.
You can also try what's called the B.R.A.T. diet - pediatricians use this quite a lot for kids with nausea, vomiting and even diarrhea. It's Bananas, Rice, Applesauce (unsweetened) and Toast (dry). It's not the most appealing diet to eat, but you aren't putting fiber or anything too heavy into your system. Here's a page from Wikipedia about it with more information for you - it also contains some other versions of this diet, as well as some contrary advice. http://en.wikipedia.org/wiki/BRAT_diet
If these things don't start working within a couple of days (I wouldn't let it go on much longer, considering how long it's been already) call your doctor to either schedule an appointment or to have her call you back when she has a moment free. Give her a brief version of what happened with your b/f and tell her what's been going on since then. Make sure you tell her that you have no other symptoms (like the ones you described) and you honestly think it's psychosomatic. Also make sure to tell her if you have done any of the things I have suggested above. She may just tell you what else to do over the phone instead of having an office visit.
Please remember that I am not a healthcare professional and these are only suggestions for you. You may decide you want to skip it and see your doc right away, which is also a good choice.
I hope I have helped. Please keep posting and let us know how you are doing.
Lots of gentle (((((Hugs))))) so as not to upset the tummy too much.
Agoraphobia, Barrett's Esophagus, Bipolar Disorder, Depression, Fibromyalgia, Mitral Valve Prolapse, Panic/Anxiety Disorders, Probable Narcolepsy, PTSD, Restless Leg Syndrome, Severe Acid Reflux, Sleep Apnea, Social Anxiety
Meds: Abilify, Ambien CR, Ativan, Flexeril, Lamictal, Neurontin, Nexium, Requip, Ritalin ER
A slip of the foot you may soon recover, but a slip of the tongue you may never get over.