But I recently masturbated using shampoo as lube.. Could this just be from that?

Sounds like soap irritation.

Shampoo is not a good substitute for lube.

Have you had sex? If so, this could be something more serious.

Either way, it's best to see your doctor.

Last time I had sex was two months ago oral probably like a month and a half ago.

While is most likely is from the soap, ( a very bad idea)

It could also be a form of STD, and you will not know for sure till you are tested, So time for a trip to your doctor or the health department