first and foremost, see a dermatologist.
also - it's possible the skincare products you use everyday could be making your acne worse. look at the ingredient lists, then peek at online lists where you can check if they could be breaking you out. zerozits.com has one ("become an acne detective") i reference often. labels that state "non-comedogenic" often lie, mostly because everyone's skin is different. i can use products with grapeseed oil, but this ingredient is a no-no for some; others rave about using jojoba oil on their faces, but it gives me huge cysts.
for more info, i wholeheartedly recommend hanging out on the skincare board at makeupalley.com. i'm a resident skincare freak over there, and we field all kinds of questions about skin conditions and request for product recommendations. there's tons of knowledge to help you out over there, including that of estheticians and derms, too.
I love, love, love the skincare board at makeupalley. I have the most finicky, stubborn, acne prone skin ever, with rosacea to top it off, and the recommendations on this board really, really helped me!
If I could recommend only two things to try, it would be the following: 1) a Retin-A type product. I use an over the counter one with retinaldehyde in it by the brand Avène (it's called Ystheal). My skin loves this stuff. 2) Every day I use a home micro-dermabrasion scrub with all natural ingredients called Epidermx II (you have to order it online). It schluffs off skin and dirt and really does keep my skin clear. You'd think it would just be hype, but no. When I'm not using this stuff, I have to fight with my face more.
There is other spendy stuff I wish I could do without but can't. (Sigh! You really do have to protect your skin.) I have found a really highly protective sunscreen that my skin tolerates beautifully (quite the feat for my skin) and which is as matte as the day is long by Sofina, but I have to order it online from Asia. I use this toner-type stuff by Bioderma called Micelle solution which I have to order from Europe. I use it every morning instead of a cleanser. It is soooo mild and soothing, and the ingredient list is incredibly short. For a cleanser I use the Laventine oil cleanser (also ordered online, but this one is at least from the States) because it gets all of the sunblock off, but I really love the Bioderma if you're not removing serious makeup or sunblock.
One of the cheaper things I use is Everyday Minerals foundation, because there is no crap in it. My face hates powder, liquid foundation, everything. Not so with this stuff.
There are good odds that you need to change skincare completely, the problem will be figuring out what you tolerate and what you don't. Try some of the stuff by Paula's Choice, I've heard people have had a lot of luck with her toners and BHA products in particular. Try moisturizing with organic virgin coconut oil (look for it at your health food store or order it online). It sinks right in, is not greasy on at all and is way better for your skin than most of the products out there. It doesn't break me out like all other moisturizers. I use this stuff all over my body.
One thing I haven't tried but which is supposed to be great is using organic apple cider vinegar mixed with a bit of water as a toner. Maybe this is similar to the lemon thing people have already mentioned?
For those who are looking to slowly heal acne scarring, I recommend camellia oil if you can tolerate it. A couple of people swear by this stuff on the skincare board, so I thought I'd try it although I was quite skeptical. I can only spot-treat with this oil because I find it can break me out, but three months of putting it on a patch of moderate indented acne scarring on my forhead has literally made the scarring half as deep. Not to mention the fact that the same amount of time putting it on my old (silvery white faded, had them since I was 12) stretch marks has faded them to half of what they were. After this experience, I will look to natural oils first for skincare needs as often as possible. Everyone says that nothing heals stretch marks, so I feel that this is pretty impressive performance for a topical solution, albeit a very gradual one. No overnight results here, and you've got to be diligent, but that doesn't bother me as long as it's working.
And for crying out loud, eat as well as you can! Try eating lots of anti-inflammatories, such as blueberries, rooibus (African redbush) tea, green leafy veggies, etc.
Whew! Good luck. Oh, I should also mention that Diane helped me, but my skin was never completely clear (I was still fighting with fairly regular acne) until I started doing all of the above.