Why Are People The Way They Are?

I (F21) have been living with my roommate... let's call him Bill (M20) for a few years while we have been studying in a new city. For the first two years we both rented a rooms that shared a bathroom in a friend of mine's house until this year where we decided to rent a basement suite. Considering how our arrangement has been in the past, it seemed smart and idealistic to move into a place that would give us some more freedom and privacy and with a person who is safe and is a low risk of having problems (My first roommate was a friend I moved in with and it was horrible). Boy have I been wrong... Some examples of what I've been dealing with: on the first day we moved in we set a schedule for showers where we would both do every second day on opposite days (Obviously flexible) and within the first two days he had three showers. He has used multiple of my kitchen appliances when we've talked about what's being shared and what isn't. I said from the first day he could do laundry on any day, but that I would really prefer Sunday. He agreed saying he usually does his Friday or Monday. well, every. single. Sunday. he has put his laundry in or left it from Saturday so that I'm unable to do my laundry. I changed my day from Sunday to Thursday and he started doing in from Wednesday night until Sunday night. He never cleans his beard shavings from the sink/counter/toilet/floor, and so much more. We've had multiple talks where we set up schedules or discussed boundaries and even more talks where I've shared my frustrations, but no matter what he always disrespects everything we talked about. A huge rule that we both agreed on was how if one of us wanted to bring someone over that we don't need to ask, we just need to let the other person know. As I'm typing, he has a person over that he never told me was coming, I saw that they used multiple of my kitchen items and food, I seen that a bed's set in the living room so they're now spending the night, and they both have been standing deliberately in front of my door playing alarm clocks and talking bad about the quality of items i own. To be clear, I've been really understanding with him as he's younger and a childhood friend... I'm starting to feel as if it's deliberate or wonder if its intentional. Every time we sit down and talk he apologizes , says he would feel the same, and promises to do better but it never works. I don't really know why I typed this all out, I feel terrible for even complaining, I also feel like I'm going insane at the same time. This is a throwaway account, thank you for reading my vent post!