The horary chart raises this possibility as Venus, the 5th house ruler (pregnancy), applies by sextile to Jupiter the Ascendant ruler (you). But before that aspect takes place Mercury aspects Jupiter. We are to decide if this works as a frustration or as a translation of light, because Mercury separates from Venus, but that happened in the previous sign, Cancer.
Mercury is the partner (7th house ruler), so the separating Venus-Mercury conjunction may well indicate the conception.
There is a 5th house - 8th house connection: ruler of the 5ht house in the 8th and ruler of the 8th house in the 5th. The 8th house is the 4th from the 5th. Are you planning to end the pregnancy if it proves to be real? Maybe at your boyfriend's advice? Some other elements indicate something like that.