On 3 separate occasions over the last couple of weeks I've experienced really painful cramps and a tightening in my lower abdomen, similar to period pain, and how I imagine early contractions feel. They each last about 5 minutes and go away as suddenly as they came on. There's no other issues, no bleeding and I'm low risk. Can't find any common denominators in what I'm doing to cause it. I've googled it, could just be ligaments stretching or should I mention it to my midwife?