I've tried to avoid giving you training advice here Emmy, as I feel it's FF's role and I don't want to tread on their toes.
Having said that, and with sincere apologies to FF, don't do any running tomorrow. Nothing. Not one step. Your reaction to your run today is your body telling you it needs to take a break and it needs a rest. You'll get absolutely no training benefit from going out and doing 13 miles, 18 miles, any miles.
You will, however, get a training benefit from not running. Put your feet up and have a recovery day. And don't think of it as a 'rest' day or a 'no training' day. It's a recovery day.
And if you need to, have a recovery day on Monday as well. Then see how you feel.
Here endeth the lesson 
PS, if FF says something different, go with their advice as, technically speaking, I'm something of an idiot.