I'm an 18 year old female and I have a severe acne problem that has been going on for about 3 years or so. What can I do to finally clear them off?

Need Rx. If it's severe, a dermatologist's visit is almost certain to help. You may be offered the oral contraceptive pill, a topical such as Clindamycin with retinoic acid, a systemic antibiotic as appropriate, and possibly even some of the big guns that only a dermatologist can use.
See a dermatologist. If your acne is rather severe, you need to see a dermatologist as you may need combination of local and may be oral meds. Like benzyl peroxide wash, local and/oral antibiotics, retinoids etc.There are other modalities like laser therapt, cumadone extraction etc.