Is 45 Yrs. old too young for menopause? No period for last 4 months. Regular pap/pelvic exams o.k.?

Bad cramps in Oct. one night, next day stomach sore from the cramps, no period. Lower back hurting at time of the month Jan. & Feb. no period. Same symptoms, just no period. Ovaries just shutting down? Read menopause can be 40 & up, average 51 yrs.old. My last period exactly the month I turned 45 (November). The last two years had missed a couple here & there, DR. said probably stress...pap/pelvic exam o.k. last June. Just no period last 4 months. Does this sound normal?? Thanks.