I am sorry to hear that you are being challenged with this worry atm. I understand how this feels.
I wouldn't be too quick to rule out allergies, as they can develop at any time...but as Chutz posted, only your doctor can give you a definitive answer on this.
Ask for a consultation, and in the meantime use your coping skills including positive/reassuring mantras...and remember the old med school adage that the doctors in training were taught:
"When hearing hoofbeats, think horses, not zebras."
In other words, a cough has many common/benign causes...no need to assume the worst.
You are going to be okay!
"Courage is not the abscence of fear, it is feeling afraid and doing it anyway!"
"Worrying does not empty tomorrow of its troubles...it empties today of its strength."
Corrie Ten Boom
Panic Syndrome recovery due to CBT