Constant Wiping After I Poop?

[19M, 160lbs] For the last 4 months, I’ve had a consistent problem with my poop, in which it is extremely soft and messy. After I poop, I have to wipe for at least 15 minutes and even then I may still be unclean. And it’s not like a little bit, it’s a lot on the paper. I can’t tell if it’s just from stress or what, but is there anything I can do? Should I eat more fiber, or change something else in my diet? Please help