How do I be less needy and so in love with my girlfriends? I

Stop depending on your partner for happiness. Your happiness depends on you.

Find a hobby, or focus on your career. Your girlfriend is your partner in life, not your possession.

Accept the fact that your relationship could end horrible, either through cheating or something else. Face this fear and be prepared for it, and you're free.

Just be a fucking man, dude. No girl likes a clingy guy. Focus on having fun and making your partner laugh. Form a connection. Don't suck the life out of her and expect her to keep you happy forever.