Second time mommas please help me!!

I get periods of immense pelvic pressure pain that last a few seconds. They have been happening for the past week or so. I am 38 weeks. Today they are happening almost every 3 minutes. They are so strong, it feels like the baby’s head is pushing down and he’s lowering himself. I have a high pain tolerance and when these happen i literally have to stop what imdoing and it makes me yell. Is this a contraction? Soo confused ! It’s happening right now as I type this. Sometimes the pain even causes it to go to my butt and I feel like I’m going to poop. Tmi I know. Sorry. But can someone tell me if this is a contraction? I am a first time mom. Not too sure if I should start “timing” them.