Advise

So I need some advise about a month ago my mom made me promise that I wouldn't date this guy he was and still is one of my best friends but I will admit he's kind of a man whore he has a new gf every other week but I never really thought much about it so anyway I told her that it was not an issue we are just friends nothing more so I made a promise. Now we have been talking more then ever and he's flirting with me slot and I flirt back it started all innocent and fun but now I actually think I have feeling for him and I met his mom and as soon as she heard my name she's like omg it's soo nice to finally meet you I don't know what to cuz I think I could have real feelings for him but I finally have a good relationship with my mom and don't want to lie to her or go back on my promise.