So I’m around 33w pregnant and sometimes I smoke at night to help me sleep...

I was going to an obgyn clinic for like 3 visits only and they did a drug test and came out positive for weed, I wasn’t aware about the test until last week when I changed clinics and they told me the last clinic left a note, now they’re telling me they might test me again randomly, I haven’t smoked since last week, is there anyway of cleaning out my system for sure besides drinking a lot of water? I just want to make sure I’m clean because they said they might get CPS if I come out dirty again, I have a 2 yr old as well. I live in Texas