@zaty: I think what's happened is you've succeeded in making your skin angry, for lack of a better term. I've always had good skin, but I've had my share of pimples along the way. It's going to happen. You will *never* be pimple-free forever! So don't stress out about a couple of zits. They will go away.
You probably don't need to use the benzoyl peroxide every day, anyway. It's kind of harsh. I'd stop using altogether, at least for a while.
I'm not a professional, but I do have sensitive skin, and it sounds like you may, also. Here's what I'd do. First, over a weekend when you're not doing much, don't wash your face with anything but plain water. When you shower, rub your face with your washcloth. This will help exfoliate it gently. You need to give your skin a rest from any products. If you get pimples, so be it. And don't wear makeup, either.
Second, if you wear makeup, make sure you wash your face *every* night to get it off. Also, make sure you use products for sensitive skin.
Third, get a cleanser (not a mask) made especially for sensitive skin, like the Simple line or Neutrogena. If you're not in the US, look for products especially for sensitive skin. Also, get a moisturizer for sensitive skin. I know what you're saying: you have oily skin. Why do you need a moisturizer? Using it after you wash your face before bedtime will help soothe your skin.
If you get a big zit, get some over-the-counter cortisone cream and dab it just on the zit. Don't use it on your whole face or you'll be right back where you were! The cortisone will help reduce the redness and swelling.
Depending on how annoyed your skin is, if you can go a whole week without makeup and just washing with plain water, your skin will thank you. I try to have at least one make-up free day a week. All I wear is moisturizer and lip gloss.
If you wear makeup, check your products and get rid of everything for your face that's over a year old. Bacteria gets in there. Replace with cosmetics for sensitive skin. If you can find Clinique, their products are awesome for fussy skin. But other drugstore lines have cosmetics for sensitive skin, too.
Don't worry about that scar. It will go away.
Treat your skin gently and good luck!