I have had horrible heartburn the entire time I have been pregnant
! I am almost 16 weeks, and it has been the worst symptom of pregnancy so far. My Mother-in-law who is a midwife suggested I try papaya enzymes. They're chewable like Tums, but in my experience they work way better, and provide relief for longer.
Sleeping propped up on a couple of pillows can make a difference as well, if you are experiencing it in the morning when you wake up.