I am a 23 year old female. At least half of the time when I poop, it leaves a big mess up on the rim and sometimes seat of the toilet. The toilet is left looking as though I had diarrhea, but I don't think it actually is diarrhea. There is no cramping or urgency beforehand that would normally come with diarrhea, and although my stool is loose and generally in lots of pieces, I wouldn't say it's as liquid as diarrhea. I don't remember exactly when this started happening frequently, but I'd estimate it's been going on for at least a couple months.
About a year ago, I started having more gas and bloating than usual, and was wondering if I had specific food intolerance(s). I thought I might be lactose intolerant, but have never been totally sure. Nonetheless, I still tend to take lactaid pills with dairy products to play it safe. But, this symptom of me always making a mess with the toilet is newer than the gas and bloating, only in the last couple months or so. What seems strange about this symptom, and makes me think that it's not necessarily caused by a food intolerance, is that this seems to happen regularly now regardless of what kinds of foods I recently ate. I don't really notice changes in it according to what I've been eating. So I wonder if there could be something wrong inside me that could need to be examined. Also, one thing I sometimes notice, is that it seems like my poop is actually messier when I did not need to go really bad (just moderately so) before heading to the bathroom. The times I need to go really bad, it doesn't always seem to spray as much. Don't know if that indicates anything, but I'm just trying to include as much info as I can think of. Thank you!

If you have not, you need to seek medical attention. Possibly a colonoscopy.

You need a referral to a proctologist who can diagnose your problem

You have already mentioned lactose intolerance as one reason. There are actually many. Dietary sugar intake increases water content in stool (this is a common problem with diabetics and loose stool). The small intestine has a limited capacity to digest certain types of sugar (as sugars in veggies or fruits). Some food for thought, so see your regular doctor and discuss your options.

You need a referral to a proctologist who can diagnose your problem

You have already mentioned lactose intolerance as one reason. There are actually many. Dietary sugar intake increases water content in stool (this is a common problem with diabetics and loose stool). The small intestine has a limited capacity to digest certain types of sugar (as sugars in veggies or fruits). Some food for thought, so see your regular doctor and discuss your options.
Forgot to mention bacterial infections as well.