should I be worried about a missed miscarriage?

I'm 4 weeks 3 days pregnant, and on Thursday I started having some pretty moderate cramping. It seemed to be nonstop for several hours, maybe with a little relief here and there in between. On Friday, I had no pain until around 7:30 at night, and it went on until I went to bed around midnight. Same cramping pain, also lower back cramps. Yesterday morning, I woke up fine, but had the same cramps and lower back pain for about two hours in the morning. I've noticed no pain ever since, and I've had no bleeding or spotting at all. I spoke to my nurse, and all she said was that cramping can be normal and I should take Tylenol. I've had an early miscarriage before, should I be concerned about a missed miscarriage? I'm just so anxious because the cramps felt just like moderate period cramps. Any experiences or thoughts?