I Had A Pimple Like An Ant Bite On My

i had a pimple like an ant bite on my neck. when i scratched it it expanded and turned darker. After 3 days, i had an out break of it on my body i.e upper extremities, a little on my eye lid and on my thighs. and around my private part. It looks like ring worm but as i research more, it looks more like Pityriasis rosea with distinct feature of Herald Patch. I don't know what to do? Can you help me?