Especially with a two-shoulder carrier that distributes the weight well, I agree that you're better off and will have less strain on your body carrying a child in a baby carrier than in arms.
Unless you're at risk of pre-term labor or have been advised by your doctor not to lift heavy weights, as long as you have the muscles for it (which you do since you have been carrying your ds) then there is absolutely no reason not to keep doing what you're doing. Especially in early pregnancy. In very late pregnancy when the relaxin starts softening up your joints, you need to be careful because it's much easier then to throw something out of alignment.