Cramping/lower back pain

I am six weeks today and have had a lot of lower back pain and mild/moderate cramping for over a week now. If I am up and moving around I don't seem to have them as much but at night trying to sleep has been the worst. I mentioned it to my doctor but because I have had no bleeding or spotting with it she isn't worried unless they gets worse. Just curious if anyone else has had this and how long it lasted?