Cramps.

Nikki • had our first baby boy on Oct.23! :) ttc baby #2
So I'm 36w5d and since about 11am I've been cramping..but it doesn't come and go, it's consistant..I emailed my doctor and they said to time them and call if there between 5-7 minutes...my question is how do I time them if they don't go away?? I tried to call nurse line but it goes to voicemail after 4:30