Herpes seems likely
rashes can take many forms -depending on the strain of virus
and the host (the patient).
It's possible you have some natural resistance to herpes, say if you already have HSV-1 the 'cold sore' virus. Herpes lesions (the rashes) usually are quite painful. The history of a new partner, and then these rashes makes me suspicious. Herpes is very common - most people don't even know they have it.