I'm 33 & I never had a mammogram done and I recently noticed I have a blackish liquid coming out my breast when I apply pressure. What could that mean?

Nipple Secretion. When evaluating a woman with nipple fluid, our first priority is to differentiate secretion from discharge. The former is a physiologic process, often emanating from multiple ducts in both breasts &usually elicited; discharge is spontaneous, unilateral, and often clear-to-bloody. While your situation does not sound worrisome, it would be best to see a breast surgeon to sort this out.
Cyst? This is often cyst fluid, but needs to be checked, make an appt with your doctor, or ob/gyn. Often breast cyst discharge is described a "machinery oil". It is most often nothing to worry about, but the only way to tell is to make that appointment! don't worry, make sure!