Hi ! I think the home pregnancy
test is not a confirmatory test to exclude a pregnancy, specially if it is somewhere else than its normal position in the uterus. From the history of your symptoms two possibilities are coming to the mind :
1) A neglected Urinary tract infection
or pelvic infection
, which has spread and causing the symptoms of a peritonism.
2) A chronic ectopic pregnancy, which might have partially ruptured and causing such pain leading to a diagnosis of peritonitis
I would suggest you to visit your gynaecologist at the earliest, who may advise you for a serum HCG test, and an ultrasound
of the abdomen to arrive at a diagnosis to decide on further course of action.