I'm 6weeks pregnant and I have terrible acid indigestion. Is it ok to take zantac, (ranitidine) I'm using Tums but they aren't helping!?

Yes. Keep taking the Tums for calcium. Zantac (ranitidine) is pregnancy category b so considered relatively safe during pregnancy. If Zantac (ranitidine) helps, but not enough, you could try Prevacid 24-hr (otc) which is also category b. Safety for either in breast feeding is unknown.