I want to celebrate my bf's birthday on the day it lands on and it doesn't seem he wants to celebrate it with me but he seems to want to celebrate it with me on the day before

As long as it's okay with him I don't see a problem. It is his birthday, not yours.

Many people celebrate on a different day mainly for convenience. He might have plans with his family, and that's why he wants to celebrate with you on a different day.

Some people don't even want to celebrate birthdays.

But to many, it is just a day, and if you celebrate it on the weekend before, or after, is often more the norm.

It probably is most likely a convience thing. If he wants to spend his b-day with you the day before, it's OK! It's his birthday, and besides maybe he's wanting to spend more time with you, and the day before is the only time. Who knows? But I'd say it's OK, even as nice as the idea to have his b-day on his b-day is...

It's his birthday so what difference should that make to you?
Some people have a birthday that falls on a Monday and they wait until the weekend to celebrate. It is not that big a deal.
This is much ado about nothing.