The problem I have with accountability partners is, you should want to do this because it is good for you. If you are keeping yourself away from sin in order to avoid exposing failure to another person, then what intrinsic motivation do you have not to do it? If you are really serious about it, then an accountability partner would be redundant. If you aren't, then your partner will not help you.
Here's some advice: I detect some self-condemnation in your post. You want to be free of the sin? Stop dwelling on it. When you fall, get back up and move on. Don't think about how bad you screwed up, don't self-flagellate, don't run from God. Repentance means turning away from something. You can't turn away from it if you are constantly obsessing about it! And it makes no difference whether you are obsessing about it in a positive or negative way. You know the old trick where you tell someone "don't think about elephants", and immediately they think of elephants? Well, by obsessing over your sin you are constantly playing that trick on yourself. If you tell yourself "don't think about sex", guess what will immediately come to mind? And if you screw up and then start thinking about how bad you screwed up, you WILL think about sex again because that is the context of the screw-up.
This isn't your burden. Cast it down at God's feet. Get up, straighten up, move on. And if you fall, do it again. And again, if you must. One thing I know for certain - from experience, and because it is a fundamental part of human psychology - you will never be free of this until you stop making such a big deal out of it.
Which brings me to my last point: Western (and especially American) Evangelical Christianity just grinds on and on and on about sex. They've gone so far as to call an absence of sexual activity and thought "purity". Well, bad news, folks. NOBODY is pure. The most sheltered child is no more "pure" than a hooker on a street corner. This is because sexuality is NOT the standard of morality. Why don't youth pastors preach sermons urgently warning against lying? Why don't auditoriums full of people take pledges against gluttony? Why is it okay for kids to indulge in violent fantasies but not sexual ones? I don't know the answer to those questions, but it is so, so wrong.
Human sexuality is created in us by God. It has its proper uses, and improper uses. Improperly used, it is sin - but sin is nothing more than falling short of perfection. EVERYONE falls short, every day, in multiple areas of their lives. A man (or woman) who masturbates seven times a day is no more or less a sinner than a child who lies to his parents, or an embezzling CEO, or a bully who picks on those weaker than himself. The habit of the Church, heaping guilt upon guilt upon guilt on sexual sin while giving only the barest of acknowledgments to everything else that a person does wrong every single day is completely backwards. The fact is, we are all sinners. The fact is, on the other hand, we are all new creations in Jesus Christ. And in Christ, there is no condemnation. Period.
What you do is not who you are. Your sin is not yours to bear. LET. IT. GO.
Not only will you see the guilt fade, you will also see yourself begin to think about it less, and the temptation decrease in frequency and strength. The only solution is to cast the burden away, see yourself for the righteous person you are in Christ, and be thankful for that.