If you ask me....You're in no position for teshuva or cheshbon nefesh or anything of the sort, so get it out of your head. Right now we have a problem. Like in the army, when a group of soldiers reach an obstacle, imagine they start bemoaning their fate! The proper approach in such a situation is for all of them to work hard together to get out of there and figure out how to advance. Later on, when all is safe and sound, they will sit in the tent together and figure out their mistakes and do better next time.
In other words, alright you messed up, alright things aren't looking good. What does G-d want of you right now? Today He wants you to be clean? Tomorrow as well? Alright, so let's work on today and tomorrow. Later on, when we're safe and sound, let's think about the past and ask for forgiveness, when we're calm and in a position to do so. Right now we're in danger so let's work towards a solution.
First thing we do is get rid of the danger. Computer you say? Get a filter. A good one. And if I asked you if you were willing to pay 15 dollars a month for the next year to get rid of your problem, would you accept? If yes, then pay for something like Mobicip or VCF, both of which I found to be excellent. (Don't get K9 it's got weaknesses).
Alright, now you can take a deep breath. But don't stop there! Me personally, I can spend as much time as I do looking up schmutz looking for loopholes and ways around the filter even to get anything to satisfy me. But that's me, so I set up a shvua fence thingy-majig, which together with the knowledge that I don't have access to anything "worth it" as it is, is all enough (thus far) to keep me nice and safe and back on track.
Another thing, one thing that always keeps me clear if I stick to it is looking some Torah, the kind of Torah that is inspiring and makes you aware of your spirituality and so forth. Now you'll tell me, perhaps, that you don't have time. But I'll ask you, as it is it looks like you might spend hours looking up schmutz anyways, so certainly you would be willing to trade that in for a half our of Torah? This is, of course, after you've already protected yourself with filters etc., so that it's sur meira, vaaseh tov afterwards.
Hatzlocho Rabbo. Keep it going, the past is fixable, but only once you're in a position to do so, right now we're fighting a battle against the Yetzer Horoh and we don't have time to stop and bemoan our predicament.