Popping noise

On my most fertile day I had sex with my boyfriend. We hadn't in about two weeks, we started out missionary but within 6-10 minutes I guess he thrusted a bit deeper or harder and it made a popping sound, with a slight pain that felt good too. Of course he didn't hear it, but I def felt it. It almost felt like he was in my lower abdominal area. We proceeded and eventually finished, then noticed spotting; assuming it happened around the time the popping noise/thrust occurred. Does anyone have any input as to what this could have been or means?
Thank you kindly.