The total change in my life

I am sick of this. There was NOTHING wrong with me 3 months ago. It all started with a vacation to Puerto Rico. When I came back a week later, I started having insomnia pretty badly. I started having "skipped beats" in my heart maybe 1 time a week. I suffered for nearly a month before I went in to see the Doc. The doc started me on Zoloft for anxiety that he thought i had. Well it cured my insomnia but increased my heart palpitations exponentially. It was so bad that i ended up with a 2 week holter monitor, ekg, ultrasound, and bloodwork. They checked my thyroid twice. After i got sick of the way Zoloft was making me feel and the heart palpitations, I quit taking it cold turkey after 3 weeks. OMG the first week i was off I thought i sincerly thought i was going to die. I felt weak, I would start shaking, terrible irregular heart beat.- in other words, full blown panic attacks. I never had one before in my life and ended up calling the ambulance. All of my tests came back normal but i am not convinced. The doc put me on 25 mg atenolol once daily and lorazepam to try and settle my heart and calm me down. It is 5 weeks later and I am still not right. Now, I have constant pain in my chest, it feels like there is always something in my throat, and i have PVC's every time i eat. Anytime i swallow anything it hurts instantly in the middle of my chest and about 30 minutes later I start having the bad Palpitations (I feel swooping in my chest, tingling down my arms, and lightheadedness) I am absolutley scared to death. When this happens to me, I cry and cry and look at my babies and cry some more. I think this is very unfair to me, and i can't help but think that this is going to kill me before anyone figures out what is wrong. I can't  think about anything else and I have so much anxiety over it that it's tearing my family apart. I can tell my husband is scared for me, but he doesn't know what to do for me. I'm afraid to do anything that will make my heart race. I am 22 years old, female, and moderately overweight. My doc insists there is nothing wrong but i know better. I would give anything in the world to feel the way i used to (even if i have to deal with the insomnia again) I just want to be happy and not scared and i want to be happy and playful around my children without crying my eyes out because i am so incredibly scared about what would happen to them if i weren't around. I'm afraid to go to sleep at night, I stand over their cribs and silently sob. i'm afraid to drive to far from the hospital, and i'm terrified when my husband leaves me at night to work 3rd shift. My hair is falling out, and i've actually sprouted a gray - at 22. I can't calm down because my heart won't stop acting up.  The only people that listen are the people in this forum. I don't have any family or friends to talk to and i'm left with the thoughts in my head on my own mortality. I can only imagine what it is like to be around me but i just dont know what else to do. i am completely lost.