1st symptom was pain in both sides of my neck, then a cough with mucas, fatigue, some nasal congestion, no fever, and chest feels heavy.

Allergy?? See your doc first. Most coughs don't require antibiotics. Your doc should get a good history and good physical exam. You might have allergy or asthma or very commonly post nasal drip, none of which require antibiotics. Or you might have a viral infection which also doesn't respond to an antibiotic. Get well soon. You can always use Jewish penicillin-I.e. chicken soup!