Aiyoh, 35 weeks adalah masa betul-betul heavy kan, so tension pada perut bawah sebelah kiri tu memang banyak ibu alami, uterus yang dah besar pressing down on everything, including that area around the rectum. A few of my mum friends complained about the same thing, especially when lying down or getting up because the weight shifts, but 3 days is a bit long lah so I'd definitely check with your doctor atau midwife just to be safe, especially since this is new for you, better to rule out anything else macam ligament pain or something yang perlu attention. Take it easy, try changing positions often, and if the pain gets sharper atau ada bleeding, jangan delay tau!