Can anyone explain this?

i really like this girl and she likes me back. i care about her a lot and i miss her, but like seeing her sometimes makes me sad? and like im normally reallllllly happy and energetic/upbeat. then when i see her my mood changes sometimes shes always happy though and like smiling and hugging me kissing me and everything sooo im kinda confused. i think its cuz i like having her tell me she misses me and cares about me cuz ive nvr had a girl tell me that soo my mood subconsiously changes because i need to fill that void of someone caring for me or i udnno if its cuz i kinda/semi dont trust what she says.