BS degree

Yes, every school I know of (although someone more knowledgable might know of a couple exceptions) requires a BA or BS before MATRICULATION to med-school. This does NOT mean that you have to have one to apply (most people apply during the end of their Junior year) but you DO have to complete your degree before you can actually enter medical school (indluding all pre-reqs).

some schools will let you enter w/o a degree, but you must have 90 hours of undergrad coursework.

While it is always possible to get in without an undergraduate degree, it is uncommon. Get a copy of the AAMC's Medical School Admission Requirements (MSAR); your premedical advisor's office surely has a copy. Each medical school, in a box on the right side of the second page, on the bottom, gives the percentage of students in the class with undergraduate degrees. Most schools show 100% or very close to it. Those with lower precentages are probably accepting students who are from special programs, arranged with one or more undergraduate colleges, with agreements to accept students who meet GPA/MCAT/Recommendation specifications and who complete at least 90 credits by the end of the junior year.
Anyway, what's the rush? Enjoy a full undergraduate education, with fun and games along the way. The rest of your life will be tough enough.