I was in H-1B status working in a company for a few months 3 years ago, and then I changed my status from H-1B to F-1 student. Now I found a job and my employer is willing to file H-1B for me, am I subject to the annual cap?

No, a foreign worker is not subject to the annual cap if he/she used the H-1B quota in the past 6 years.