Stretch marks😔

Sorry if TMI.. but i'm 30 weeks pregnant and have got just awful stretch marks all over my butt.. they go further down than the picture shows, it pretty much covers the whole thing. Does anyone else have this or have had it with previous pregnancies?? Did they fade for you?? I don't have stretch marks anywhere else, just there. I don't understand why, my butt hasn't even gotten much bigger. I didn't have any stretch marks before I got pregnant.

EDIT: I've gained around 30 lbs so far, and I gained almost all of it during the second trimester. I've only gained 2 pounds so far during the third. I weighed about 152 before I was pregnant and now I weigh 182.