Is it possible to expand my Nostrils or nasal cavities?

Hello,
Thank you for your question. I encourage you to meet a couple of experienced Board Certified plastic surgeon for a detailed physical examination. Since you appear to be suffering severe breathing issues that can be adressed only by the surgical nose job. A proper assessment is needed since reasons could be various such as nasal valve collapse, deviated septum or enlarged turbinates. To find out more please visit our RealSelf before and after pictures. 
Best Regards 

thank you for posting your question. Although breathing problems can have many reasons, your issue might be related to the internal and external valve of your nose. You performed yourself a so-called cottle test, which related to the internal valve. Supporting the internal and external valve when a rhinoplasty is performed usually corrects the problems you are describing. Nonetheless, a in person consultation and exam is required for a correct assessment and final treatment plan. I hope this helped. Kind regardsBianca KnollFrankfurt, Plastic Surgeon

Hi and welcome to our forum!From your history, especially with improvement noted when mechanically pulling your nostrils outward, it appears that you have obstructed nasal breathing from valvular collapse.  Without photographs, I cannot determine the source. Small nostrils can impede airflow as well as collapsed nasal valves internally. In addition, a crooked internal nasal septum or enlarged turbinates may contribute as well. These entities can be corrected with rhinoplasty. Spreader grafts can support the nasal valves. Septoplasty can straighten the septum. Turbinectomy in selected cases can improve nasal breathing. Photos are required to determine the nature of the small nostrils in order to determine the proper treatment. Temporary placement of plastic tubes in the nostrils has not proven successful.Visit a board certified plastic surgeon for in-person evaluation and discussion.Best wishes...

Hello and thank you for you question. Well I don't see any photos of you cause you didn't add but the problem you describe makes me think of "internal nasal valve disfunction". Which can be fixed with some special surgical technics. Beside that, you may also have "external nasal valve disfunction". 
I suggest you for a consultation with an experienced plastic surgeon.
Best regards