Dear Lily~I saw that no one had responded and I really feel for you during this trying time. First let me say, at age 26 you will not die from this condition/problem. You did the right thing by seeking medical attention. I was a mother who breastfed both my children. After one year of age, I weaned them. You are placing yourself in a very physical and emotionally demanding state by breastfeeding a 3yr old toddler AND a newborn at the same time. I am a total supporter of breastfeeding, but truth be told, it requires you to be in good shape physically and at times can be draining. That is why most give up and bottle-feed. My advice is to wean your toddler and continue breastfeeding your new baby. That alone, could improve your hormonal state and possibly your anxiety as well. I am a huge believer in Ativan. It works wonders for anxiety, has been around for decades and is safe for many conditions. I am not sure if it passes thru breastmilk however. To keep up what you are doing, you have to eat well and sleep well and be on top of your game. That is not easy with a toddler and baby to care for. Your tachycardia may be a sign you need to slow down or revise your schedule. Try to invite a friend or relative over to watch your little ones so you can take a nap~or~maybe getaway for a little bit to the mall or park if you feel up to it. Sleep deprivation causes so many problems, I could not begin to list them all. Anxiety and blood pressure problems are definitely two of them. I hope you will take a much needed break. It would be good for you and your kiddos.
Best of luck on your next appt.