This really doesn't sound like poison ivy all over you. It's unlikely that it would spread like that after so much time. Besides, it's not a rash and it itches anyway. It's reallly more of a systemic reaction and that tells me you need to heal from inside.
It's probably too late for Tecnu - that's what you use right after exposure to remove the oils from your skin, but I would think that, after weeks of showering, those are gone. FYI there is an astringent you can use when the blisters are fresh, it's called Domeboro (available over the counter but sometimes behind the pharmacy counter) - you mix it in water and put wet compresses on the blisters. It draws out the water and stops the itch.
There is a natural anti-inflammatory called lunasin - the most concentrated form is call LunaRich X which is extracted from the plant via a mechanical process (never a chemical one). You need a referral to the one company that has exclusive rights - message me and I will give you my last name and my ID number, and I'd also be happy to talk to you more about it. Totally safe for pregnant women because it's purely food-based in a vegetable capsule. It's also available in some nutritional products that are, likewise, safe for children, pregnant mothers, people with suppressed immune system (e.g. cancer, autoimmune diseases). You say you are highly allergic and maybe you can message me to tell me more about that - that's probably remedial as well through non-drug means. All my allergies are gone.
You could take an outmeal bath or a cornstarch bath too, assuming you aren't so late in your pregnancy that they are telling you not to take baths at all. Try not to rub any more cream or lotion on anything - the rubbing can aggravate the itching, and there may be something in the creams that is irritating you.