Smoking

So today me and my SO got into a huge argument. Probably the worst one we've ever been in so I was having a bunch of anxiety like to the point where I just felt like my body was shutting down and I couldn't handle it so I took a hit of weed to calm my nerves. I haven't smoked at all throughout my pregnancy and now I'm feeling so beyond guilty about it but it felt like the right thing to do because I couldn't calm myself down and that was the only thing that worked. I'm not sure if I should come clean to my doctor or just not say anything since I don't plan on doing it again. Any advice? I'm 32 weeks pregnant. I'm not so much worried about one hit hurting my baby. I'm more concerned about cps. I don't know if I should come clean to my doctor or would that create more problems?? Btw I live in Northern California and I'm almost positive it's legal here now