Thanks for the query.
As you are having irregular periods
it is difficult to guess the time of ovulation.
So though you are having some symptoms of pregnancy
just by them we cannot confirm or rule out the pregnancy.
As some other conditions as you told PCOS etc. can present with these kind of symptoms.
So you once consult gynecologist, get examined and go for ultrasound
By this the possibility of pregnancy can be rule out and also the possible cause for your amenorrhea
can be made out.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429