Mate, I've got them in the same place, they're just stretch marks, they lighten up a lot over time, but then it's just time to make some more, shows you've been putting in the hard work !!
I've heard of people having success with using Bio-Oil to get rid of stretch marks but haven't tried this myself as I'm quite proud of mine haha.
Best of luck with whatever you try to do, whether it's get rid of them or create more !!