What Causes Heart Palpitations And Shortness Of Pregnancy Post Child Delivery?

I am12 weeks post partum, entire pregnancy was normal, perfect delivery and such. At 2 weeks pp I started having heart palpitations, shortness of breath, and lightheadedness every so often. I initially blamed it on sleep deprivation and not eating enough. I was finally able to eat more and have been getting at least 8 hours of sleep every night for the past month. However, about 2 weeks ago, all of the previously mentioned symptoms have gotten much worse and much more frequent. I have gone to the doctor, they performed an EKG and discovered I have arrhythmia. They ran blood tests which came back normal. I have also been excessively hungry and exhausted lately despite eating and sleeping enough. Consuming high amounts of sugar seems to help briefly, but after 30 minutes or so the symptoms worsen once again. Any ideas?