Rash on forearms and halfway up arm

Help?! I'm 16 weeks pregnant and I developed this rash on my right arm that started in a small patch the size of a kiwi. It's now spread to my forearms and halfway up my arms. I've been putting aloe Vera lotion on it and trying not to scratch. I thought they were going away so i scrubbed them with a wash cloth in the shower last night and clear liquid pus started coming out of the bigger ones. I'm getting a little worried since they haven't gone away. I first got the rash on Thursday. I don't have the rash anywhere else.  Can I use hydrocortisone cream and take Benadryl?