Almost getting walked in on while having sex

Ka
Ok so my girlfriend and i were home alone because it is a half day for our junior year and we were at her house. So we started having sex, while she had finished i had not and then when im being very loud her mom comes through the front door at 12 and says "whats up" and i was being pretty loud and i think that she heard me. i was stuck there untill 3:00. Then i was freaking out like what the fuck just happened and my girlfriend was just apoligising over and over again. It was so embarassing. So when i was on my way out her mom gave my the dirtiest look ever like imagine the look of ur exs moms face as if u were breaking up with their child in front of them. That is the look she gave me as i was leaving! Ugh so much more embarassing than if she were to walk in on us because we would at least know that she saw something. But we know nothing ughhh. So my question is what should i do?