Look up pictures of scabies and read about them. I've treated my entire family for them twice over the past 10 years and each time it took us and our pediatricians considerable time to figure out what it was. It's easily treated with cream and house cleaning....our worst sympton wasn't the rash as the rash wasn't always there...but the itching was. It was UNBEARABLE after a shower or in bed at night when our skin got warm. Supposedly the temperature change makes the scabies start moving around and causes the itch to be intense.
Another thing you may consider is Bedbugs...they look similar to ticks and you may or may not see them between your mattresses, in the sheets, under your bed and inside your mattress and boxspring....they are making a major comeback in the USA. The bite looks like a mosquito bite and is extremely itchy. You will be driven to scratch them until they almost bleed. The fix is to find them and identify them...and if you find even one just assume there are thousands more inside your mattress and BURN it. I'm not kidding...Burn it and get a new mattress, scrub down your room, and definitely look up bedbug treatments online and follow the directions. For some reason doctors seem more intent on finding an allergic reason for your itching and bumps and often overlook that it may be an infestation of some type.
I even had a daughter that suffered with pinworms for over 2 years with numerous doctor visits complaining of feeling something moving on her anus and poking her inside her vagina at night causing her to wake up and scream...it wasn't until I actually spotted one of the VERY tiny worms that I called the doctor and she was treated with one pill for pinworms...and the problem was gone immediately and so were the sleepless nights waiting for her to wake up crying about the poking sensation.
I'm not saying that you don't have an allergy or some other issue but don't rule out the little buggers that can very easily take up residence on our bodies no matter how clean you are. Good Luck!