How do i tell a girl my feelings?

You see i dated her in the 5th grade and now i am in 6th this year and she is in 5th but befor i was in 5th and she was in 4th i know it sounds crazy dating a younger girl but she looks old as a 6th grader anyway we dated then on movie night i dumped her ever since then i just cant stop thinking about her i was thinking about buying a single rose and a small box of chocolates and leaving them on her door with a note that says for (name) something like that or i would meet with her in school like in the 6th week of it at recess and tell her how i fell but heres the problem i broke up with HER whoch by the way was a big mistake and i use my friend which is my x's cousin using 3 way on her cell and she says that i broke up with her and theres no way i can get her back but alot has happened since then we went to some block parties together she says we are friends but we dont hang out alot like we are nervous to talk to each other any advice would help