The same thing happened in ME2 when I thought I'd take a stab at Garrus and in the end I was romancing Thane. No offense to Garrus because he is awesome, but Thane just struck a chord with me. Maybe I have a thing for tragic endings lol.
I could never justify Thane as a romance if I had romanced Kaidan in 1. Though I did love him immensely. He just seemed more like I was going to confession talking to him and there wasn't enough time to know him. Where as Garrus, I knew, I trusted, and he was my BFF. If I am going into a suicide mission with a broken heart, let me be in the arms of someone who really knows me. They sealed my Garrus love though with that Tango and Citadel DLC. If not for Raphael Sbarge sneaking me back with his voice, Kaidan would be solo all the time LOL
So, as much as I already have my scope on Cullen, I have this sneaking suspicion someone is going to steal my heart with their personality. It's why I talk to everyone. I want to know them first and foremost, if I didn't I would have hated Morrigan. She was mean to my Alistair and could be cold. Very different from my light hearted rogue. But that last conversation with her, I wanted to hug her. I'm a sucker when someone calls me their "sister".
I bounce between Fenris and Anders, I can never make up my mind. I get wicked jealous when Isabella and Fenris flirt, even if I am with Anders, and want to scream "Back off Bestie or I am gonna sick Aveline on you!" haha. Maybe it is my affection for Elvish, I dunno, but Solas has me doing the squinty eye thinking there is something about his personality that I am going to want to wrap him in a blankie and feed him cookies while Cullen looks disapprovingly at me.