For a long time I convinced myself that I was unlovable. It had a little bit to do with the way I was brought up. With two parents that were busy cycling the drain with their own problems, it wasn't really important to ever make sure that their daughter's emotional needs were being met with any consistency. I faded into the background at home unless either one of them decided to take out their anger on something that I'd done, and I attempted to solve that problem by desperately trying to make everything perfect.
Real, emotional love terrified me. Philophobia is the academic terminology. I didn't know what it was, or how people experienced it. The first time somebody told me they loved me in high school, I was actually physically nauseous. I spent the better part of my teenage years getting into relationships that were purely about physical expression. Making out, blowjobs, fingering, but never ever saying things like, "I enjoy spending time with you." This continued into college. When a woman and I went on a "date" (like dinner, dancing, keep all our clothes on type of date), and she sent me a mix CD the next day, I just thought, "how cool. New music to listen to." It never crossed my mind that somebody might genuinely enjoy being around me, that somebody might think about me even after I wasn't there.
I took a personal vendetta against "normal" relationships. "It's okay! I'm just in this for the sex." Not that I didn't actually really enjoy sex, but there was a conscious part of me that was intentionally separating it from any actual feelings. If I was in it just for the sex, then the people I was with were also just in it for the sex. I slowly started justifying those all-your-clothes on type dates because I knew it wasn't because anybody gave a shit about me whether I had clothes on or not; that I would eventually not, and that was the appeal.
Then I slipped. I met a fantastic man who genuinely did care about me. I tried to keep it purely about the physical, but I slipped once during sex and said, "I love you," instead of "I love this." (We'd been together for about 2 months at that point.) He stopped mid-stroke and I immediately started crying. Then he hugged me tight and said, "I love you, too."
It's been an interesting journey since then. I still don't really believe in love, but I've at least allowed myself to feel it. (If you will, I'm a bit of an agnostic about love now. I recognize that it could possibly exist, but I still don't think it has much effect on me on a daily basis.) That's an argument for another post.