constant nausea!

Hi Ladies, since exactly 6 weeks I have been experiencing constant all day nausea.  I t:ry eating crackers every couple of hours but it doesnt help much. I put lemon in my water which helps at first but then I get heartburn from the lemon and feel worse. Tried ginger ale but doesnt do much. I hate to complain, as I have had 3 previous miscarriages at 4 weeks and am so excited to be 7 weeks, but this constant nausea is wearing down on me...even moreso when I think it will go on for at least several more weeks. Help anyone? Thanks!