Why can't all pregnancies be the same?

This pregnancy has defiantly been a nerve racking one for sure. I wish all pregnancies were the same so you would no what to expect.
 A couple of weeks ago I started having heart palpitations. I mean strong ones it was hard for me to sleep I had to sleep on my back, (which is hard enough for me when I'm pregnant anyways). It felt like my heart was going to jump out of my chest that's how bad it was and it was happening every few minutes all day every day. So I finally called my OB on Feb 27th since it has been happening for a week to see if it was normal during pregnancy because it has never happened with my other pregnancies. I did have them a few years back but the cardiologist said I was fine and normal healthy people can have them some are just more sensitive to them then others. But since I am pregnant it scared me even more. So my Dr. told me to go see a cardiologist cause how often I was having the episodes was not the norm for pregnant women.
Then on Saturday we were watching t.v and I got up and my heart started racing, my left hand and arm was tingling and I was scared I did not want to have a heart attack. So Tyler took me to the emergency room that night. They gave me an I.V fluid, did some blood work to see if I was anemic, or had thyroid problems and a few others but I don't remember what. They also did an EKG and it showed that I was in sinus Tachycardia but of course no palpitations. The results came back and everything looked good so they decided to let me go home considering I had a cardiology appointment on Monday.
Monday came and again I wasn't having very strong or consistent palpitations but the cardiologist wanted me to wear a 24 hr halter monitor to see if they could catch them. (Now I know how Kenzie felt when she had to wear them annoying. The funny thing is, which seems to happen when you complain about something then get it check out it stops doing what it was doing).  He also wanted a follow up echo the next week.
Today I had my echo and my heart looked perfect. The halter did show signs of the palpitations but it was at the top part of my heart which wasn't very concerning to him. So I am happy to say no symptoms of palpitations since after the halter and my heart looks healthy. He just wants to see me after the baby is born to make sure it still looks nice and healthy.  Now to continue to pray that the baby is growing happy and healthy.
What a roller coaster!!!