Please help on Visa

My situation:
1. My wife is a student in USA (F1)
2. I am a landed immigrant in Canada.
3. I applied for F2 VISA in ottwa. They gave me B1/B2 (1 year valid with M entry).
4. I tried to enter USA twice but was sent back because I do not have a job.

Question?
Can I apply for F2 again while my B1/B2 is still valid. They told me if I have F2, I do not have to have a job to enter into USA.

Your advice is appreciated.