So you've been running for about 4 months and still having pelvic issues? I would definitely talk to the doctor about that.
I didn't have any pelvic pain when I started back (just some bladder issues) but I was able to run throughout the pregnancy, so I don't know if that comes in to play.
As for speed, I'm sure that comes along with how often/far you're running. I did a half at 3 months pp and I certainly wasn't PRing, but I was faster than the 1/2 I ran during the first trimester by then.
Again, this might have to do with the fact that I ran throughout the pregnancy - It makes sense that people who ran while carrying an extra 20something pounds at the end of their pregnancy would be faster after the 20something pounds came off.