Thanks for asking in Healthcare Magic.
Your symptoms may either be due to pelvic inflammatory disease
or bacterial vaginosis
. Birth control pills can result in irregular menstrual flow or complete absence of period after stopping them, they may not result in abdominal cramps and discharge..
The increase in weight in your lower abdomen area may be due thickening of endometrium that is common in delayed periods. Multiple negative pregnancy tests does not necessarily indicate absence of conception as the reliability of home pregnancy tests
varies unless you do it meticulously.
So, it is always safer to exclude pregnancy through blood tests or through physical examination by a Dr. You should consult a gynecologist to confirm the diagnosis and to rule out pregnancy. You may need antibiotics or anti fungal agents depending upon the type of infection.
I hope this is useful to you.