My menstrual cycle is so unpredictable I never know when to expect it. It is never monthly and once I didn't get my period for 6 months is this normal?

Doctor can evaluate. There are many causes for irregular menstruation. One common one is polycystic ovarian syndrome (pcos), a hormonal imbalance along with cysts in the ovaries. Though most irregular menstruation is not acutely dangerous, any woman who does not menstruate monthly should consider seeing her pcp or an ob/gyn for evaluation.
No. The gyn md needs to examine you and find the cause of the irregularity of your menstrual cycles.