Uy, go see your doctor ASAP though, kahit 6 weeks pa lang, mas better na checkup na ngayon to make sure everything's okay, especially with your second pregnancy!
Once your OB gives the go-ahead, most of us moms just follow what they prescribe, they usually recommend specific brands na okay for pregnancy and some really don't have that "rusty" aftertaste you're worried about. A few of my mum friends swear by the ones their doctors recommended from the start kasi less nausea, less weird taste. Your OB will know best which brand works nicely for you, sis, don't worry, maraming options na available na walang weird lasa ngayon!