I've been having some pretty sharp pains in my lower abdomen for the last three days. Gets pretty…

I've been having some pretty sharp pains in my lower abdomen for the last three days. Gets pretty bad when i walk around. Anyone else experience this? Have a dr's appt on Tuesday and will be 18wks on Wednesday. Could this be round ligament pain? Started when i was 15 weeks but havent had them till this weekend.