is this too weird??

Brittany
So my mom is 35 and divorced and she has this friends who's 26 and he's at my house all the time and me and him started spending more time together and I got a huge crush on him (I'm 18 btw) it's really obvious we flirt and my mom kept telling us to not do anything together and I just assumed it was our age difference and the fact that he is her friend but then I started suspecting it was more than that so I asked my mom about it and she told me they hooked up a year ago but it was just one time and nothing and at first I was super pissed he was flirting with me knowing he had been with my mom but after a few days we were back to flirting and ended up having sex and I still have a huge crush on him so I guess I'm asking if that's really weird that I like and slept with a guy my mom slept with a year ago I mean I never think about it and my mom has a boyfriend who lives with us and I don't worry about it but is it weird to other people?? And also I'm worried about this becoming something serious and then having to tell my mom and it sucks sneaking around so much should I just go ahead and tell her??