Hi and welcome!
I just looked at your pictures and she looks like a normal pregnant yorkie to me. It is not unusual for the nipples to change color during pregnancy. She looks like she's got quite a belly full; please keep us posted on your xray results..........post xray pics if you can.
Yes, there are a few of us expecting April litters, myself included. My girl is due as soon as this weekend. Please join us with your updates in the April litter thread here:
http://www.yorkietalk.com/forums/bre...r-litters.html