Hi,
Sometimes it takes a few months to get regular after the pill. How long were you taking it? I was on it for 7 years and it took AGES for my cycle to become regular afterwards. My sister-in-law had a similar experience, she only had 2 periods in 8 months after stopping the pill.
Maybe you could start doing ovulation tests to find out when is the most ideal time is? If your irregular you may have to do them each cycle.
And with the doctors, I was ttc for 8 months and the doc still wouldn't investigate. But you may find one thats a little more helpful.

my periods have always been like this though when i first every got them i didnt see them again for about a year then i got them again and it was the same thats why i went to the doctors and she put me on the pill and they became regular really fast.
i was on the pill for about 6 months and as soon as i stopped because we where trying for a baby they disappeared again...
iv been off the pill now for around 4 months im pretty sure if that helps at all...