Trying to Conceive: 6 Months, Still Trying Community

Could she be pregnant? My fiancée has shown some signs of early pregnancy. She typically has regular periods, and consistent symptoms associated with her period a week prior. The last week of September, she had a late period (5 days or so), then some spotting one day (very light), and then nothing. She never showed her normal premenstrual symptoms at that time. About 5 days after that, during intercourse, I noticed more spotting (brownish-red) on my penis, which she was also surprised to see.


Since then, she has expected her most recent period to be normal. It has not arrived yet (about 12 days late now). She has had some strange cravings, and a little difficulty sleeping, but nothing to write home about. She rarely eats meat, and was eating slices of ham late at night! She took a HPT last night, with a negative result. I was not present, but I asked her a few questions afterwards. She said that she drank a lot of fluids prior to the test.


Note: She has been off of birth control pills for 15 months for medical reasons. We occasionally use spermicide, but not all the time, since it is uncomfortable for her. She has never wanted to get a pregnancy test before, despite being late in the past (always associated with a dosage change in her anti-seizure medicine).


Question: What is the likelihood, if any, that she is pregnant with a negative result from the HPT? How long should we wait before testing again? Thank you all in advance for your input!