Sorry, I agree that if you're going to get them you're going to get them. I have used Palmers Stretch Mark Cream, Mamma Mio Tummy Rub, Bio oil and This Works shower wash since Day 1 (and before I was pregnant, moisturised my whole body daily) and I have got loads. I didn't have any on my tummy until over 30 weeks and then they came on in full force.
That said, it's got to be worth a try - perhaps they'd be even worse if I hadn't done anything. At least if you use stuff you know you tried!!