Hi Harding,
I hate to say it but it does sound like it could be herpes.

The symptoms you describe sound consistent with herpes and the circumstances sound suspicious, although it might be other things too. I think it's good that you're going to get tested tomorrow. You should probably talk to your ex-bf too, so that he can get tested on a new sore or by taking a type-specific blood test. If you can afford it, you might want to get blood tested tomorrow too.
Good luck. Let us know how you make out and what the doctor says. I hope it turns out to just be something like an ingrown hair or something.
TheOneInFour