Copper
"Paragard was the first BC ever used at 27yrs old, after my second child. The first 3-6 months were horrible heavy periods but they adjusted to heavy bleeding the first 2 days of my period... 
Everything was going great until 2 yrs later, now 29 out of no where I started feeling heart palpitations, trouble breathing, sweating. I figured it was high blood pressure and scheduled an appointment right away. I'm perfectly healthy but was asked to get lab work done and also asked about my birth control....Doctor told me that IUD's cause heart palpitations. 
Lab work came back with mild Anemia, so now I'm really bummed out because I no longer feel safe with these BC options, but also after doing some research, heart palpitations may persist after removal."