It depends on which meaning of personal you mean. If you mean the 'belonging to me' personal, I probably wouldn't say any of them.  It is your room so you expect the belongings in it to be your personal things.   It depends on what was said before the sentence but I might say this: There is a lot of stuff in my room. If I've already mentioned that it is my room, I'd say this: There are a lot of my personal belongings in the room.    However, that is assuming that by personal you mean 'belonging to me'.If you don't mean that but instead are using personal to mean 'private', then your sentences make more sense. If you mean private things that you don't want other people to see, I'd probably use 2 or 3. As Ethan said, the 1st one seems a bit more formal.

They all sound good. Another option; I have a lot of personal belongs in my room. or I have many personal belongings in my room.

THanksa lot

I think that all are common, and all sound really natural! 1. is the most formal, so 2 and 3 might have a tiny bit more use than 1.

I vote 2.