Dear Sammie,
I do understand your confusion.
Since such irregularities in your menstrual period are repeating every now and then, the chances that you are pregnant are very poor. It seems you are having
hormonal imbalance. Please get your blood examined for FSH, LH, Oestrogen,
Progesterone,
Prolactin (These are all reproductory hormones). In addition, get your Thyroid function test done on your blood (T3, T4, TSH). Also,
ultrasonography will give a good clue for any pathology. However, I do jot feel you are having PCOD as in this condition, the menses are delayed and heavy.
There is nothing like left over from previous menstrual cycle. Uterus cannot hold some part of the bleeding inside for a week or more. I feel after these tests, you should report with the reports to the Gynaecologist for further investigations if needed and the treatment.
This picture and history you have narrated does not fit into the picture of
pregnancy.
I hope, you have got relevant, important and useful information with advice.