4 weeks excruciating back pain


So I just found out I’m pregnant this last weekend, 4 weeks. Everything seems good till today. I have excruciating lower back pain, it’s start with just when I bend down now it’s whenever I move, walk, and bend. I’m worried it could be something horrible. Anyone ever have this happen? Please help! I don’t have an OBGYN yet so I haven’t been able to ask anyone.