When did you begin to get your stretch marks during pregnacy?

I'm 17 wks Im still -3 pounds for my pregnacy weight but my bellys big all my weight has shifted to there it's jello like and not firm is that weird considering I had almost no fat on my tummy before and Ive gotten 2 stretch marks on my belly in 2 weeks is it to soon for stretch marks does that mean my bellys gonna get really big and I'm gonna have alot of stretch marks? I've been useing palmers tummy cream (coco er) and palmers stretch mark and scar faider