I just had a baby in July. I also have IBS-D and have had it for about a year & a half now. I've had all of the proper testing to rule out other possibilities that may cause the diarrhea everyday. When I was pregnant, my diarrhea never "stopped". I'd say that it slowed down a bit...but I was a "nervous nelly", as I typically am, through the pregnancy, so go figure!
Have you ever thought about having Small Intestinal Bacterial Overgrowth? I'm thinking that it may be my problem. It is when you have too many "non-helpful bacteria in your intestine vs. the good bacteria to have proper digestion. My Dr. just put me on some antibiotics to see if it helps the diarrhea. I'm still awaiting the outcome...this was the first full day of taking the antibiotics. It woundn't hurt to research SIBO a little bit!