I agree... This is my first but I have been reading a lot due to not getting too much helpful info here, and the discomfort and cramping are our little signs of what's to come : ) Just let doc know.
This is what usually happens at this stage of pregnancy, i just had my 3rd baby, and from week 37 til 39 i had tightenings and period type pain. Nothing turned into proper contractions tho, i ended up being induced due to placental abruption. From now on, you will experience these until you give birth. Good luck!