I can understand your frustration, but you should stop this line of thinking, and if you really do mean that you don't see the point in life anymore, than I think you need to make an appointment with a therapist asap. Don't let depression pull you under! Your baby needs you. As for your heart problems, I think you've got your own answer here, though maybe you don't quite realize it yet. If you don't think your doctor has it right, seek another opinion.
Wow that was quite a post....and i should finish that with partum as in it sounds like you are going thru postpartum blues like all moms do up until about a year after your child is born so you need to find a way to deal with this and recognize it for what is happening to you. Your body is readjusting back after the pregnancy and is super busy getting your hormone levels back where they belong so especially with two little kids your life is worth living and you need to get pro active and deal w. all of these issues that you feel you are having....you are the only chance your kids have on this earth as their mom so you need to step up to be there for them like we all had to. The first suggestion that i have for you is are you seeing your regular doc for this or your OB/GYN? If you are not a good idea...you need to make an appt. with a heart doc so that you get the answers you need. I am very sure and i too would be as frustrated as heck if everyone basically told me that its not my heart its my mind especially if i know what i feel. Personally i have no idea how fast fast is as you didn't post what your pulse rate is when you say its a fast heart....remember normal is between 70 and 120. Anything can set these episodes off including hormones which are battling in your body fighting their way back to where they belong right now and your heart is also adjusting to not having all of the weight and pressure under it from the baby...so be a little patient. You need to rule everything out that you can w. a heart doc and if in the end they say its nothing after testing then you are going to have to trust them and deal with the anxiety issues. I know its tuff especially having two little ones at that age but it sounds to me like you are a great mom and are just straight out frustrated and thats what happens when we can';t get a straight answer. There seems to be two conclusions here...number one call the OB/GYN and tell them you may be having issues with the post-partum and secondly call a heart doc...spend the 50.00 to get the answers so you can move on, live your life and raise your kids.Remember as we all post here...caffeine, coffee, colored sodas, chocolate, energy drinks, tea, any of those things set them off as well as not sleeping well at nite....time to get moving my friend and take back your life....