As you said you are 5kgs overweight
, that itself can cause menstrual irregularities. Obesity is a vicious cycle which causes lot of hormal disbalance. Other causes of menstrual irregularity can be stress, anxiety, tuberculosis
I also want to know if by any chance you are still feeding your child. Lactation can also cause delayed menses.
Some females have a condition called premature ovarian failure
where there is early menopause ie before 40yrs. its very rare though.
PCOD cannot be just ruled out by ultrasound. You need to get Serum LH and FSH levels which can also tell you whether its a case of premature menopause
where FSH levels would be high.
Genital infections can also cause menstrual irregularity.
To regularize your periods you can take progesterone
tabs for ten days a month which will help you have menses on time and you can conceive also with them as they are not contaceptive. For knowing proper dose and time of taking these tabs ,you need to consult a gynecologist personally who will advise you according to your last menses date.
Irregular menses do create problems in conceiving but they dont cause absolute infertility
. SO you can try for pregnancy as well. Keep taking folic acid
tab which will help you conceive.