Been using the cleanser twice daily for a month ... haven't really seen any changes in my skin?

When using Differin gel it make take weeks or even months before you notice improvement in your skin. Your acne may even get slightly worse for a short time when you first start using the medication.
see http://www.drugs.com/differin.html

How to Use Differin
* Apply the medication after cleansing your face with a gentle, non-soap cleanser. Gently blot dry your face with a soft towel before application.
* Apply the medication to areas affected by acne once daily before bedtime or as directed by your dermatologist. Use the amount directed by your dermatologist – using more than the recommended dosage will not speed or improve results buy may cause irritation.
* To apply the medication, spread a thin film over all affected areas. Avoid contact with the eyes, lips, angles of the nose and mucous membranes. The product should not be applied to cuts, abrasions, eczematous skin or sunburned skin.
* Call your dermatologist if you experience any skin irritation or any other problems.
* While using the medication, avoid exposure to sunlight or sunlamps. If you must be in the sun, use non-comedogenic sunscreen with an SPF of 15 or higher.
* Do not stop using the medication without first alerting your dermatologist for further instructions.
* Return to your doctor’s office for follow-up visits as directed by your dermatologist.
* Avoid using new cosmetics, cleansers, moisturizers or sunscreens besides those approved by your dermatologist. Make sure you use cosmetics labeled non-comedogenic.
* You may begin to see results in 8-12 weeks. Your acne will improve with continued use. Regular use will clear existing acne and help prevent new pimples.

During the first few weeks of treatment, itching, dryness, redness, burning or peeling may occur. Exposure to sunlight, including sunlamps, should be minimized during the use of Differin Products. Use of sunscreen and protective clothing over treated areas is recommended when exposure cannot be avoided. As with other acne medications, overexposure to extreme wind or cold, or use of irritating skin care products may aggravate the skin.
from http://www.differin.com/

Hang in there and stick with it.