I guess i don't know how to be in a relationship

I'm in a long distance relationship with a girl and we are gonna meet soon (we already know each other).
She's been very busy and stressed with work and she ends up taking that on me.

Now talking about me, I'm a lonely and needy person and i always feel the need of someone showing their affection, so i feel too attached to her as she does care for me but she's not showing it anymore.
Lately every good or bad thing she does has a huge impact on me, and this is terrible cause i know nobody should ever put their happiness on someone else's hand.

I feel so ashamed to admit i'm lonely and needy, but i would like to find a way not to depend on her this way, it's terrible. I suffer and she gets annoyed by that. then i feel worse and she stays with me cause she worries. and this cycle is so unhealthy for us.

If you guys have any advice i appreciate.