I have been dealing with that as I trained for the princess half. I went to our local running store when they had a free screening by a sports med doctor and also had a physical therapist there. Here are the things I have been advised to do that have seemed to help:
-freeze a water bottle and roll your foot over it a couple times a day for about 20 minutes.
-stretch your calf muscle - don't over stretch your plantar fascia - just concentrate on the calf muscle
-use a massage ball - got one of those at my running store - little green ball with knobby things on it - just roll my foot over that in the evening
-doc said to take 2 alleve in the am and 2 in the pm - he ended up later giving me a prescription for naproxen - just a little more than the alleve dosagee
-Strausburg sock - use at night - got this at my running store as well - it is a little hard to get used to but it has seemed to help - it just keeps your foot in a good position while you sleep
-sports med doc also gave me a night brace because I didn't like the sock at first but the brace is WAY more uncomfortable so I went back to the sock
- never walk around barefoot - ALWAYS wear shoes - I got some dr.Scholls inserts at walgreens for PF and put them in a pair of
crocs that I could get on easily or would wear my running shoes with inserts.
-there are also exercises the physical therapist gave me to help strengthen my foot/plantar fascia - I need to do these more
You also may want to have your shoes/inserts checked to see if you are wearing the right ones.
So sorry you are dealing with this - it has been rough for me - my training for the half was not what I had hoped but I was able to finish and my pain isn't nearly as bad as it had been so some of this stuff must be helping. Back when it was really bad i was also told to lay off running for a few days - he also told me after the half to take it super easy and let it rest. Hope this helps!!!
Kori