Swelling & itchy skin


So I'm 36 weeks pregnant and my feet,legs,hands and arms are swollen and have become very itchy the past week. I have told my Dr. about it but he doesn't know why I'm so itchy. can I please have some advise on what it could be or what I can do to help it. I've tried benadryl, soaking in a tub, and itch cream none of it seems to work. please help!! NO RUDE COMMENTS OR BASHING PLEASE!