Oh dear, I don't blame you for panicing. I also developed a rash shortly after going on lamictal, same dosage. It was limited to one thigh, halfway up from the back of my knee, coming around to the front and angling down to my kneecap. It was slightly itchy, red, raised patches that were slightly scaly. I thought I had psoriasis, as it runs in the family, but after a biopsy by a dermatologist, it was somewhat uncertainly named lichen planus, origin unknown. Let's hope that's what you have because steroid cream cleared it up completely, never to return in over three years taking lamictal. It did take several months to disappear completely, but it was harmless. It might have been a coincidence that it started soon after starting lamictal and that could be true for you, too, as your doctors say.
Since you've already been researching, I'll mention another skin rash associated with lamictal, but actually, many drugs can cause this, even over-the-counter preparations. I'm positive this is not what you have because it comes on very suddenly and is a life-threatening crisis with a few hours. It is called Stevens-Johnston, or something very close to that. However, no one should just take my word on it, best to talk to your doctor. I, too, did the research when my rash appeared. If you come across this while surfing, it can really scare a person. I spoke to more than one doctor about it and was assured that if I had it, I'd know it right away by the rapid and severe development. Still, forewarned is forarmed and we all need to be acutely aware of potential risks with any drug we start taking. I hope the dermatologist is able to diagnose you soon so that you can rest easier and receive the appropriate treatment. I did not have to go off lamictal and I really hope this will be true for you , as well. Please keep in touch and let us know how things are going. Dealing with side effects is certainly difficult, just adds to our challenges. Good luck with this and especially with your pregnancy. Blessing Waters