What can cause me to have to force myself to breathe? i thought it could be anxiety but it's happening when i'm calm.

So many questions : So many questions you need to answer. Like how old are you?are you a smoker? Are you taking any medications? Do you have any allergy?do you have any asthma?most likely you are congested from allergy,start taking medication for that and clear your sinuses. By the way you do not have to be anxious at the time of difficulty breathing and still could be panic attack.see your doctor