I'm really excited to have discovered this site - wish something like this had been around five years ago! (I'm sure both of those are common sentiments.)
The short version of my story is that I've been struggling with the problem since around my Bar Mitzvah (about 10 years ago). Being the computer expert in my house I was able to have free reign of the computer, and I took some pretty horrible advantage of it. I went through phases of staying 'clean' (when I was about 16 I started a daily diary-style log, and created a program that counted weeks, days, hours, minutes, seconds, of staying clean, which was an effective tool for a while.), and then failing multiple times in a row. As a good hard working, and disciplined student (B"H) my double life tore me apart, but it took a long time until I finally felt I had it under control to a significant degree. I found other 'softer' time-wasters, like relatively innocuous films and tv shows to download and watch - although that too was at odds with my sterling reputation in school. In my final year of high school I got involved with an early Frum blogging-style group (before there was even such a word), and formed a number of online friendships including some girls, which I think helped keep me clean, and very much helped me stop objectifying women. I certainly wasn't very good at limiting my online time then (often staying up to inordinately crazy hours of the night), but I barely had any Ta'avah to seek out p.
About five years ago I left home for Yeshiva, where I again had no problem (much more limited computer access). Coming home for Bein haZmanim, I was fine - my online friends were still around and I often stayed up to ridiculous hours, but I was clean (Quote from my log: "Seconds: 58,594,770 (Do I still need these for any reason? Life has certainly moved on, and I certainly think up... "). However at some point, I slipped - not the first time I was home, but I think the next one (there's a strong correlation to the fact my other online outlets - my IM acquaintances - had for the most part moved on in life to other things), and since then *every* time I've been home for Bein haZmanim I've failed - sometimes earlier, sometimes later. (This Sukkos, it was really only on my last day home that I ended up staying up past 5am browsing everywhere I shouldn't - it was during that session that I first stumbled across this site, though at that point I was too far gone to pull out). The problem isn't directly related to the availability of a computer either, because for the past year I've had a laptop in Yeshiva, and whilst in Yeshiva itself, I haven't really had a problem. (With some minor exceptions - I'm actually on my guard right now, that I might be prone to acting out, as a kind of residual from my Bein haZmanim failure.)
I think this issue has wrecked my self-esteem and confidence in multiple areas - something I'm especially noticing as I begin Shidduchim. My main problem though, is how to tackle it during the time when it's not a direct danger. The after-effects are definitely around for at least a few weeks or more after falling (with terrible images popping into my mind during Davening, learning, etc.), but generally BH I don't feel any real Ta'avah to go where I shouldn't when I'm online (though I do recognise a problem I have with staying online for longer than I should). At one point I went so far as to reveal the problem to my parents (over the phone, one Elul Zman), but I don't think they realised the gravity or the depth of the issue - they understood it more as a problem haunting me from my past (which I suppose I keep hoping it is), then as something I need help with now. Any advice would be much appreciated. I would be happy to be an accountability partner, and could probably do with one myself, although again, as mentioned my main challenging times are during Bein haZmanim, (or other times that I am in a more isolated out-of-Yeshiva setting for more than a weekend or so).