Breastfeeding and consuming

I have not smoked or consumed any marijuana basically since I found out I was pregnant. I smoked once about halfway through (maybe a puff or two) but I know smoking in general isn't good for my baby so of course I didn't mind not doing anything. Obviously I wouldn't smoke around my baby or put him in harm's way, but I have questions about breastfeeding and weed. I've heard of pumping and dumping although being a first time mom I'm not too familiar with it. I personally do NOT see it hurting my son even if I didn't. Being a first time mom, I don't know what kind of tests they will run on my baby at his regular checkups. I can't see doctors running unnecessary drug screens on a newborn but one never knows. I'm particularly thankful for this group now more than ever because I can't imagine posting this sort of topic in the regular forum