Based on your situation, testing negative for HIV with a fourth-generation test 73 days after possible exposure is quite reassuring. The window period for this type of test typically ranges from 4 to 6 weeks (around 45 days) but can extend up to 90 days in some cases.

Given that both you and your child's mother tested negative around the same time using more advanced tests like those from Roche Diagnostics, it does provide strong evidence against an HIV infection at that point post-exposure.

While results are generally reliable at the stage you were tested, healthcare providers often recommend retesting at the three-month mark (or roughly by day-90) just as an extra precaution since there may be rare instances where seroconversion occurs later than expected. It's essential to follow through with any recommendations made by medical professionals regarding future testing or monitoring.

Overall, while it seems promising based on current information, following up with another round of testing if advised should help further confirm these initial findings and offer peace of mind moving forward. If either of you have concerns or questions about next steps or additional reassurance before reaching full conclusiveness feel free to consult a healthcare provider who can guide you effectively in managing any lingering uncertainties related to potential HIV transmission risks during your past breakup scenario.