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!