I would certainly not worry about the weed you smoked during the first 15 days of your pregnancy. However, if you're worried about it, you could quit for the rest of the pregnancy. Kinda an 'up to you' thing. My personal opinion is that I'd be more worried about the laws in regard to children. That's the main reason I stopped. Too much anxiety in having weed around and worrying about getting caught and possibly losing my kids and definitely my job.
Medical Marijuana: A Surprising Solution to Severe Morning Sickness - Salem-News.Com
Mom booked, baby born with marijuana in system | NORML's Daily Audio Stash
as a side note... there's NOTHING more effective for nausea. I used medicinally during both of my pregnancies. Some days I wonder (hehe) but my children have no type of brain damage.