Natural remedies for heartburn in pregnancy?

I'm only seven weeks pregnant, so I'm sure it's not the baby that's causing the heartburn, I think it's because I have such bad morning sickness, I'm throwing up all day, and when I have nothing left in my tummy to throw up it's just acid. It's really uncomfortable, and I really don't need heartburn as well as extreme nausea. I've been told by the pharmacist that I'm ok to take Rennie's and Gaviscon, but no other over the counter remedies as they are unsuitable for use during pregnancy, but the awful, chalky, disgusting taste of these tablets makes the sickness even worse. Is there any natural or herbal things I could take that wouldn't harm the baby, but would get rid of the heartburn? Thanks in advance.