I've had a lot of sex over the years and gone steady with a few.
It's hard to say if they where significant tho.. I did fall madly in love with one person, it wasn't worth the drama in the end I truly believe we are better off having gone our separate ways.
Anyway that relationship just started out as them being bored and kissing me after hanging out for an evening. I often think of them as soulmates. Even if we weren't meant to live out our lives and eternity together. We probably wanted to meet up in this life.
Also a triggerish one.
I've had a few sexless relationships with ppl I really care for and we met at school, or work, or in the Army. They all sorta helped complete me at the time. And two housemates, one I really loved and also was terrified of. I miss them though and wish I could make it up to them and let them know how wonderful they are.