Please How Do I Get A Bump-free Butt? It’s Darker And Really Not That Smooth, Maybe Due To Rashes I Had Before

i tried applying mild astringents and whitening lotions to the area and it improved a little. but when i stopped doing that nightly, it went back to its “old self” again. this skin started to really darken after giving birth to my youngest child. usually around the anal area and pantylines are most affected. i tried wearing thongs (to let the skin breathe and prevent further irritating the area) but to no avail.
its not itchy but i noticed that when i wear tight-fitting jeans or panties, that’s where the problem starts. . . at first its like a pimple or a mild irritation. . . then it becomes a “boil” (i dont know if that’s the right term for it). . . and when it “pops” and dries, it causes scars. sometimes it reaches at the back of my thighs, so i find it difficult to wear short-shorts for fear it may “peek” out.
as much as possible i can only afford lotions or creams or any toners. no plastic surgeries for me please.
only affordable options as i dont have any work for now. . . thanks. . .