Hello,
We define primary infertility by the inability to conceive even after 12 months of unprotected intercourse. Try having intercourse around ovulation and if still you are unable to conceive, then get the various causes causing it ruled out.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
You should deffinetly go see your doctor. It is not normal not to have your period for 4 months unless you are pregnant, they will advise you what to do next.