Hi notimeforlove
could be so many things - I'm in a similar situation without the post nasal drip and sore throat - but the rest could very well be allergies, it could be stress, I guess there's a possibility of STD, but I'm not a doctor and I would suggest you get yourself off to one fairly quickly so you don't keep worrying about whatever it is and start getting treated.
I am currently being treated for allergies and infected hair follicles (including itchy armpits), but I'm female, so I don't have the beard lol.
I get lots of random itching - some due to meds, some to allergies - let your doc work it out.
Best wishes.
Deb