Faster heart beat coz your heart is pumping more blood to supply baby. Faster breathing is also normal due to hormonal changes causing you to breathe more deeply, taking in more air. I think also bcoz uterus compresses our lungs and caused us to feel breathless. I'm 36 weeks and I feel this way almost everyday since 3rd trimester. Until baby lightened, or dropped lower into our pelvis, we'll continue to experience heartburn and breathlessness.