13 weeks pregnant belly seems smaller than yesterday?! HELPPP!?

Hello :) i'll be 13 weeks pregnant tomorrow, and yesterday you could actually tell I was pregnant and I could feel my uterus swelling and it was noticeably larger. Now today I don't look like I am showing at all and my uterus just feels squishy. I am wondering doctors or past/present pregnant ladies is this normal?! This is my first pregnancy and I am really worried. I do have a doctors appointment on Friday but I can't wait that long! Thank you for any answers!