Pain in the Butt and Heel

I've been having a couple of nagging pains.  The first one is in my heel and it started on Monday.  I went ahead and ran on it Tuesday and Wednesday.  When my run date for yesterday texted to cancel, I took it as a sign to give my heel a rest.  I'm pretty sure it's some form or level of plantar fasciitis.  It's not too bad but I definitely want to eliminate it as quickly as possible.  It hurts the most in the mornings, seems to 'warm up' during the course of the day and doesn't seem to hurt at all when I'm actually running.  It's a new 'injury' for me so I'm going to have to do some research to see what, if anything, I can do to alleviate it. 

My second pain is, literally, in the butt.  As I've mentioned before on this blog, I'm currently doing a 30 Day Ab Challenge.  I quickly realized that I need to tuck my feet under something heavy.  The only piece of furniture in my house that is both close enough to the ground to properly hold my feet down and heavy enough to counter my beefy 133 pounds is an antique armoire.  As you can see in the picture below, that armoire is located in a room with marble flooring.  Marble is HARD.  I've found that I need to pad the tops of my feet with a towel and I have a yoga mat folded over and over to four times the normal thickness.  And that's still not doing the trick.  My tailbone is absolutely killing me.  Tonight, I think I'll try a folded up towel on top of the yoga mat and see if that provides any relief...  but I'm about to give up on this part of the challenge because it is just too painful.  Anyone have any suggestions to make sit-ups less painful? 

Not great picture...  but you get the idea!