Breathing problems can be totally normal in late pregnancy because your placenta has grown so much its pressing on all of your insides, including your lungs/diaghram. But if youre concerned about it, definitely call your doctor or L&D
While pregnant with my son I also had an irregular heartbeat. Turns out I had a heart murmur. The doc said its harmless and nothing to worry about. It can happen due to the extra volume of blood in our bodies during pregnancy.