Stretch marks

I had just a few pink stretch marks on my hips, outter thigh and inner thigh now I'm going to the gym more and loosing a bit a weight they seem to have gotten longer but still pink. I'm keeping them well moisturised but they don't seem to shift or fade.  I'm not really that fussed about them because I'm most likely to have them when I become a mummy. But I'm just confused to why they have got longer?