Is this labor?!?!

I’m 36 weeks pregnant today and The last 3 days I have been having extreme menstrual like cramps that are constant for hours at a time. I’ve noticed when I’m at work they are a lot worse until I get home and can sit down. (I work in a kitchen on feet 8 hrs) Last night I woke up to Braxton Hicks and cramping. I timed them but only had 2 and then they stopped. Now tonight I woke up again not Having Braxton Hicks but severe pressure and cramping in lower abdomen. I tried to sit up in bed and it got worse. Has anyone else had these pains? Are they the start of labor? My last appointment I was not dilated or anything that was 1 week ago. Also not sure if it relevant but the baby has been measuring 3 weeks ahead the last 2 ultrasounds that I’ve had.