Same thing is going on with my heart....my heart is pretty healthy, i have no problems or anything. The only thing I can suggest is asking your dr to check to see if you are anemic. I became anemic with this pregnancy and i had to take ddifferent prenatals and an extra iron. And I'm actually less tired since i switch and i do have more energy. And my heart still does all that, but not as often.
The heart issue I have the same thing and I have a healthy heart, and my chest will get numb feeling pain with it and I'm tired more too I'm 32 weeks and 5 days.I was told it's normal but I'll be asking my doctor at my next appointment.