Is it weird to call my professor something different every time?

My favorite professor. Every time I address him, I use a different salutation. Sometimes it’s Dr. Firstname, sometimes Dr. Lastname, or it’s Professor Lastname… and once I ever went so far as to address him as Professor Firstname. But that’s only because he signed off with his first name in a very warm farewell email. (This is my second class with him) And I felt that Professor Firstname is really tasteless, so I probably won’t go that route again.

Do you guys think the professor finds it weird?

I think I’d stick with Dr. Lastname or Professor (with or without his last name).

^^ I agree. Dr. or Professor followed by Last Name is the appropriate way to address a professor unless he/she invites you to use his/her first name.