Is my teeth crowding moderate or severe? (Photo)

You have extremely underdeveloped jaws and severe crowding.
I would suggest looking into Epigenetic orthodontics to expand your jaws and make room for all your teeth,

Ira L Shapira DDS, D,ABDSM, D,AAPM, FICCMOPast Chair, Alliance of TMD OrganizationsDiplomat,  Academy of Integrative Pain ManagementDiplomat, American Board of Dental Sleep MedicineRegent & Fellow, International College of CranioMandibular OrthopedicsBoard Eligible, American Academy of CranioFacial PainDental Section Editor, Sleep & Health Journal
Member, American Equilibration SocietyMember, Academy of Applied Myofunctional Sciences
Member, Academy of Cosmetic Dentistry

Hey, thank you for posting the photograph. Invisalign can most definitely straighten your teeth. If you need a quick fix, I would advise to remove one tooth from the lower arch. the treatment time will still however be atleast a year. This is the most natural way to fix your teeth. 
All the best!