You meet a guy and have sex with him within 2 weeks of meeting him...

You meet a guy and have sex with him within 2 weeks of meeting him, you don't bother to get to know him, you are not friends with him on social media and at this point you are just having sex. Neither party has expressed interest in a relationship past what it is but you low key start having feelings for him and want more but he just wants sex. So you start seeking to find out more about him and finds he has a gf or someone that he is really into (but you are not sure which it is). What do you do next? Tell the other girl you 2 have been involved or leave well enough alone?