I did something rather bad, should I confess?

I told my mom about a masturbation problem I've had, and made a promise to her to lay off pornography. I have pretty high moral standards, and the fact that I was pleasuring myself to such objectionable materials made me feel extremely guilty and stressed, so much that I begin feeling intense stress-induced headaches. I couldn't stand it, so I prayed for forgiveness and immediately told my mom about it. We set up a plan of sorts to help get me off it, and I stopped looking at porn for about a week-and-a-half. Now last Friday, I began feeling tempted to look at porn. I mainly used my iPod Touch to get material, and thankfully my mom took advantage of the restrictions settings and blocked off Safari. Unfortunately, the Wikipedia app I used had an update which allowed you to browse other MediaWiki sites. One of those sites was Uncyclopedia, which had an article on boobs that had more than a few arousing images on it. I gawked for maybe a minute, then my dad popped into my room. I jumped at his sudden appearance, then promptly went to another page. He asked what I was looking at, to which I lied and said I was reading a page on some web program. He then began questioning more, saying things like "What were you really looking at?", "Are you behaving?". I, of course, lied to him each time. I loathe the idea of lying to my parents, so this struck me pretty hard with guilt. About thirty minutes later, my mom came into the room and asked me if I was looking at porn. I lied again, and this is what really made me guilty. I feel so awful to have betrayed my parent's trust and to have lied to both of them, and have begun feeling stressed and guilty. I tried to simply repress the guilt by saying that I know what I did was bad, I'll try not to do it ever again, etc. It helped the guilt, but it certainly didn't help the stress. I've begun having minor tension-headaches (aside from my usual sinus headaches). Today, however, I started masturbating but stopped before I came. This added to the stress and guilt, and makes me feel even more self-loathing. I am considering confessing this Monday, but with it would come severe consequences that I simply wouldn't be able to bear: I'd more than likely having anything Internet-related taken away, I'd lose all trust with my mom, and I'd probably get a curfew. As much as I don't like the idea of those punishments, I will take them willingly than live on with the knowledge that I lied to my parents. I merely need reaffirmation. Should I go through with my plan and confess to my mom on Monday, or should I continue on and forget it? In my current mindset, there's really nothing to to stop me from confessing. Also, I'm 13.