I'm 24 and have never had a normal period cycle I can go 6 months without it and I use no protection and am still not pregnant the doctor said I had a cyst on my ovary 4 yrs ago but it has gone now what is wrong with me?

This is something that you will have to go back to the doctor for. Unfortnately you may get some good advice here, but it will all be guesses.

Since we cannot do a physical exam and a complete medical and family history it is virtually impossible to tell what is wrong.

When was your last female physical? You should be having 1 every year after you become sexually active.

Please make an appointment with your physician.