What kind of labs are you getting done?
You should tell your current gf exactly what you said here - that your ex wife said at one time told you that she had herpes, that you totally forgot about it because you never got any symptoms (I'm assuming that's what happened).
Now, you've had some symptoms of itching, tingling and red spots, and your doctor thinks it might be herpes, so you are getting tested for it.
This is all quite plausible, by the way. If you do have herpes, it's absolutely possible that you wouldn't have known until now.
That said, this doesn't sound a lot like herpes. It could be - I don't know what the red dots look like, but it could be eczema, dermatitis, an allergic reaction, etc.
Make sure the blood work you get is a type specific IgG blood test.