Cramping and lower back ache

Hi everyone! I'm 5 weeks today and ever since I got my positive test (9 days ago) I've been experiencing period like cramping off and on every single day. It's mostly in the evenings and through the night. Lasts about 1-3 minutes at a time but sometimes it's pretty uncomfortable. No spotting though at all. My doctor says its normal but it freaking me out! Anyone going through the same thing?