It could be your uterus stretching. I told my midwife about the same type of pain I was having and she told me to make sure I was drinking LOTS of water. I've found it definitely helps!! If the pain gets worse though, I'd definitely call your doctor.

My mom said that the beginning of her labor started that way. She never had back labor and said in the beginning it just felt like really bad menstrual cramps.

welcome to my world, girly! sounds like you are starting to get somewhere! yay! make sure to drink plenty of water. if you are resting when they happen, get up and move around to see if they stop. if you are up and around and they happen, rest. my nurse also said to eat some bread or pasta to make sure that my sugar wasnt too low and causing the pains.

have you ever felt your belly to see if it gets tight when you have the pains? it could be a contraction (braxton hicks) or just a normal part of pre-labor. ive been there for a few weeks.

ahhhh! im so excited for you!

My Aunt told me this is how her labour started too.
There is no tightening with the pains, I had a few braxton hicks last week and my uterus got rock hard but none of that with these pains.
I see my DR on monday so I will mention that to them. At 37+3 no-one has even mentioned checking to see if I am dialating or engaging yet so I will mention this to the doc.
Fingers crossed I am on my way :)
Thanks for your replies