Stretch marks?

I am fairly a good weight, not too skinny and not too chubby either but in the middle, i am 5’4 in height and recently started noticing both my hips have developed stretch marks overnight? I dont have any on my tummy but quite big and obvious ones on my hips? What could this be due to? I don’t believe i am pregnant i am ttc but not regular with my periods? My diet is good I don’t think im over eating? Has this happened to any one before? I didn’t have any stretch marks previously so this is new to me