I had a similar problem years ago, but I was a meat-eater at the time.
I would describe the pain as sharp, stabbing, like something were poking my insides with a toothpick. The pain was over as quickly as it began. I'd put it as a 3 on the 10 point pain scale, only because I couldn't help but gasp out loud, even going halfway to the floor in pain.
Then, .5 seconds later, and its gone... like nothing happened
After a few tests, it was called "intestinal spasms."
Basically, something made the smooth muscles and nerve endings in in intestines get upset, and they contracted, or cramped up.
The problem is a lot less severe since I went vegan.
I makes sense that any major change in diet could cause this. Your poo is a lot different now after a lifetime of eating habits.
My non-medical-qualified advise is to relax. Its good that your doc is checking everything out, and not making assumptions. But, I feel the odds are in your favor that your body is just freaking out a bit. Your intestines have done things a certain way your whole life, and now you're asking them to change.
Get your tests done to make sure, but I'm sure you're fine.
And get used to pooping more often! Attachment 15265