It sounds like you have a fairly significant problem with acne
. The causes of acne are complex, but the most important factors are a change in the levels of androgenic hormones in the body which stimulate the production of skin oil (known as sebum). This skin oil is produced in pores in the skin. If these pores get clogged with keratin like material, a pimple forms. For a while we thought this process was effected by diet. We used to think that eating greasy foods or chocolate increased the number of pimples someone would get. We now know that diet (including coffee) does not effect your acne. There are few things you can do, other than medication treatments and time that can help reduce your acne. Most people start with over the counter benzoyl peroxide cream as the first line treatment for their acne.
You should also see a dermatologist
. The advantage of seeing a dermatologist is that they can start you on more aggressive medications such as topical and oral antibiotics and topical retinoic acid. These are very effective treatments. If these do not work, then the dermatologist will have the ability to start even more effective treatments such as isotretinoin. Good luck.