Hey gyane_mara, according to USCIS, the list of degrees that fall under STEM are:
Actuarial Science. NCES CIP Code 52.1304
Computer Science: NCES CIP Codes 11 .xxxx (except Data
Entry/Microcomputer Applications, NCES CIP Codes 11.06xx)
Engineering: NCES CIP Codes 14.xxxx
Engineering Technologies: NCES CIP Codes 15.xxxx
Biological and Biomedical Sciences: NCES CIP Codes 26.xxxx
Mathematics and Statistics: NCES CIP Codes 27.xxxx
Military Technologies: NCES CIP Codes 29.xxxx
Physical Sciences: NCES CIP Codes 40.xxxx
Science Technologies: NCES CIP Codes 41.xxxx
Medical Scientist (MS, PhD): NCES CIP Code 51.1401
STEM Designated Degree Program List is based on the US Departmen of Education's "Classification of Instructional Program" (CIP) 2000 report which you can find online at
http://nces.ed.gov/pubs2002/2002165.pdf
See the list and find if your major falls under STEM or not.