Glad to hear you're not going to risk it. :) Also glad to hear you're planning to breastfeed as long as you are--Too many mothers don't bother to breastfeed at all and it's a shame!
I have tripped with the little one a few times and gave him pumped milk or formula...and was fine to nurse towards the end of the trip, every time, with no ill effects. I do pump and dump first though. at this point most of it is cleared out of your system. in fact, most of it is out by the time you even start tripping. I honestly don't think it would affect a baby at all anyway because they perceive reality a hell of a lot differently than we do. but since most people will think I'm Satan for even thinking such a thing might be possible, I'd say to give him a bottle while tripping to be safe. I must warn you though that tripping after having a baby isn't as much fun. even if you get a sitter, its hard, and I don't recommend taking much. its hard to explain but you can't really "let go" when tripping if you're a new mother because you feel like you're leaving your baby behind. its frustrating because you can't not let go because a substance is forcing you to, but you don't want to so you don't feel like you're leaving your baby by himself, which causes an extremely emotional internal struggle. being unable to breastfeed intensifies this. I can barely even smoke anymore. but I will say that if you can handle it, do it. my son is the happiest, healthiest, most vibrant little ball of joy and wonder that I've ever seen, and I attribute that to beneficial substances consumed before/during pregnancy and nursing... judge me all you want, but my son is alive and well! don't like what I do? don't do it...lol hope that helps love...!
