I'm itching all over my body and it won't stop.

32 F, 5'4 139 lbs, Caucasian, nonsmoker, occasional drinker, no recreational drugs. I take MyFembree for endometriosis.

About 3 days ago I suddenly started itching all over my body, particularly in my hands, scalp, and legs, but also in other places as well. There is no rash and nothing about my home or daily routine has changed. I didn't start using a new laundry detergent, travel, go swimming or hiking, pet an animal, or eat or drink anything new.

I've never experienced anything like this before, and the itch is so bad that I wasn't even able to sleep. I went to the ER on Monday morning, but the doctors didn't run any tests and only told me to take daily antihistamines. I've been taking Benadryl and loratadine and they do help reduce the itch, but I can still feel it. I'm not having any other allergy symptoms, like runny nose or sneezing.

I'm reading stuff online about how this can be a symptom of certain blood cancers like lymphoma and leukemia, but I feel like if I go back to the ER they just won't take me seriously. I have a specialist doctor that I see for my endometriosis, but I don't really have a PCP. What should I do from here? If this is a true allergy, I have no idea what's causing it. And if it's something else, I don't know what tests I need or who I should visit next.