How can I tell my friends I don't want to go out?

I'm supposed to be going out with a couple of friends today, we've postponed going out for about a week due to bad weather and one of them working awkward hours.

I did want to see them, but last night over Facebook they said they hate me(I honestly have no idea why) one of them called me a hateful *****.. afterwards she said she was joking, but hate is such a strong word, and I don't find it very funny.

I think I'm quite sensitive, I can't help it, it's just me. They know this, ,yet they still say hurtful things. A couple of months ago this friend said she hated my face. She's so confusing and gives me mixed messages. :/

I don't want to see them now. I feel sick because of what happened last night. Thankfully my boyfriend was there to calm me down though :/

So , how do I tell them? I've not been great anyway, , but I don't like making excuses.

Thanks :)