I've had my share of being uncertain and such. One of my friends who I nearly ended up dating caused me quite a bit of teenage depression for quite some time. Right up until my current girlfriend. And she's not the only one who I ended up being depressed about (though the second one was me being stupid and not reading the signs).
Long story, I'll try to shorten it a little. The day Rebecca (girl #1) was going to ask me out, after 6 months of friendship, walking home together after school, talking about all sorts of stuff including really philosophical type stuff, I was working myself up to ask her out, considering she would by my second girlfriend, I had quite a lot of nervousness to try to work away, in any case, on that very day she was gonna ask me out, some guy named Eric, a real looser douche who was just trying to get down her pants, asked her out, and she said yes. Of course, that lasted about 2 weeks. I even ended up giving her some advice. I didn't know him well, but the way he was around her, I though he was just trying to get down her pants, and a friend confirmed it. Now, I tried hard to keep friends with her, I had classes with her, and saw her fairly often, though not quite as often as before. A couple months, and boyfriends later, I got an email saying telling me that she had planned on going out with me that day, which of course, made me depressed, considering that she was A) the only person who I just randomly went up to and said hey to, in all of high school; All my other friends I met through other friends, and B) one of the only girls I knew who wasn't from my old school and didn't make fun of me. Now, by this point she was going out with a guy named Ryan, who I didn't like at first, and didn't seem to really like me much, though that may have been my imagination. She ended up dating him for a long time, but he was a terrible influence on her, and she got really into heavy drinking, drugs, and partying. They were engaged for a time, but he was too possessive (understandably, considering she wanted to go to parties he wasn't at, and he didn't really trust her). In any case, she's completely changed now, and even that causes me frustration and pain because I constantly wonder what she would have been like if she hadn't gone out with him, if she'd gone out with me instead of Eric. If that would have made a difference.
Girl #2, Danielle, though I always called her Dan. Amazingly, we met on Lycos Chat. She randomly whispered me asking about where I lived and shit. I didn't really care, but said that my town was a pinprick place about 2 hours north of Toronto. She said go ahead, she may know the place, though I doubted it. I told her anyway, and she said she knew it. Turns out we went to the same school, and such. We began talking about teachers, what we were doing in school, and we RP'd (roleplayed through lycos chat) a lot. Eventually, we ended up meeting, and hanging out in person. This was when I was still really depressed and shit, and at the time, I wasn't looking for a girlfriend. We became good friends, despite her being 2 years older than me. (Which was kinda unusual, all things considered.) Well, after going to a number of movies together, getting rides home from school, and stuff like that, I ended up meeting my current girlfriend. I originally met her online, through a friend, and we talked about anime for a while, argued and such, but became good friends. I ended up asking her out in an email (yes, I'm that bad with girls), and I'm not sure whether I'd even met her in person at the time. Well, at the time, I hadn't realized that Dan was interested in me so much, so she was quite noticeably upset after hearing about it. She refused to talk to me and avidly avoided me for a long time, and it did take a while for me to figure out what she was unhappy about. This led to our friendship being destroyed, because a couple months later, she ended up going off to college. I still feel bad even now for this one because she was such a good friend. I really didn't think something like this would hit her so hard, but I really feel bad. It was especially awkward because I didn't really want to explain why I was depressed at the time to my girlfriend (who still barely knows the story), because it's kinda awkward to say "well, a good friend of mine isn't talking to me because I'm going out with someone other than her."
So yes, I've had my share of depressing problems relating to girls. Both of those still bother me, even now. I will always wonder how things might have turned out if I'd made a different decision. Both girls who liked me are out of my life, and for me, that's a big issue, because other than my girlfriend, and my childhood friend who I don't speak to any more, they were the only girls to actually like me.
This wasn't meant to be a "oh, you think your life sucks" post, but a "I sorta know what you mean" post. I just needed to get this out there, because you guys are about the only people who know the whole story.
All of this took place between early grade 9 (I met Rebecca in September of grade 9) till about April of grade 10.