Mom, I'm not a virgin

Carly
How do I tell my mom that I'm having sex?? I'm a senior now and I've been lying to her face for 4 years and I kind of feel like it's too late to tell the truth.  
I feel bad for lying to my mother and I know [now] that's she wouldn't flip out knowing I'm sexually active, but HOW  to I tell her?? I hate lying to my mom and I want to tell her the whole truth. I'm pretty sure she knows already, because she's not an idiot and she's known all along, but she's just waiting for me to own up and tell her the truth?? 
If I told her my bf and I have been having sex, I would also be telling her that I've been lying to her. And how would I keep having sex with my bf if she knows when/where (I know she'll ask)
I'm not sure if I should tell her at all. Or if I DO tell her, how do I bring it up ? 
I love my mom, but I also love dick 😂😂