How to stop heart burn whilst pregnant?

I have the WORST heart burn, it radiates to my back and i’ve been to my doctor about it – before I feel pregnant and she said it’s quite common. Now I have it and it’s so painful, I’ve taken about 8 tums I don’t think I should take anymore, what else can I do?!
Can I take prilosec whilst 1st trimester – it’s the most pain I’ve ever been in…. help!