As others have said, that does sound normal, and the pinkish stuff is probably blood. I had discharge like that for close to a month, and it was definitely worse after dilation (when it mixed with lube). In addition, dilating puts pressure on the bowels - I wasn't used to thinking this way, either, but the dilator is basically being stuffed into a channel that runs directly alongside the bowels. I found that using the bathroom beforehand did help with dilation, but I wouldn't be surprised if the inverse were also true (dilation making the intestines feel/act a little weird).
If you had a fistula, the last symptom you'd have is constipation, as it's basically a hole that makes it impossible to prevent feces from leaking out.