Heating pad while pregnant?

Alyssa • ✨ Mum² 🎀 🏈 ✨ Fiancé to a keeper 💍
Is it okay to use a heating pad on the lowest setting for my back? I'm 5w6d, and my back is KILLING me. I've read mixed reviews about heating pads during pregnancy, and I've heard that they are bad for fertility in general... Thoughts?