Was late a week & 1/2 last month & again i am 3 days late this month with horrible right side pelvic pains but neg test... what could it be?

Need evaluation: by an experienced healthcare provider. The horrible right sided pelvic pains could be due to an ovarian cyst and/or pelvic inflammatory disease (PID). PID can be very dangerous and lead to scarring of the tube and problems with fertility. PID is most commonly caused by a sexually transmitted disease, but can result from other infections that are not sexually transmitted.