You my friend is having anxiety attacks. I have had the same issue before and and went to the ER thinking I had a heart but it was just a panic attack. A heart attack and panic attack are almost the same which causes confusion in a lot of people which leads them to the ER. If you left arm is all numb up and your chest feels tight like an elephant is sitting on you making you can't breath then you are having a heart attack. Also acid reflux or heartburn gives you that chest feeling as well. In that case just drink a full glass or milk or take some antacid.
Also the reason why your doctor prescribed you to go on lexapro is because he probably thought you were depressed due to seeing people having heart attacks and then thinking that you might one day have one too. My doctor prescribed me that too when I told him the same condition that you're having. Hint of advice stay off antidepressant they do not do anything but make things worst. Relax and destress yourself the natural way.
its funny that I came across this post because in the past I've seen people go into a heart attack and seizure and now everything that happens in my body makes me feel like I am having the same. Just relax :)
Hope I have helped ya. If you have any other question you can send me an e-mail on here.
You feel insecure because of being alone for long periods of time but here's one thing I will suggest, do you have a relaxation routine you do on a day to day basis? If you don't, you should do this quite soon. When you are in a calm state, the emotional centers in your brain are quiet, and the more analytical centers function at their peak. So when you are in a fully calm state, and you feel a little pinch or ache somewhere around your chest, you can basically note the feeling, dismiss it and that over time I think, will help you to naturally realize the pains are nothing related to your heart - they're minor and annoying little pains.
About these little pains: Are they deep or shallow? If they are shallow, they could very well be minor muscle spasms or intercostal pain from your ribs. You can get this aching or infrequent pain right on your breastbone sometimes because the cartilage in chests sometimes get a bit inflamed from overstretching our arms when working or cleaning and it can be disconcerting and mistaken for our hearts when it is just our ribs or pectoral muscles. I too still get this little ache or pinch per se, but it is a shallow pain (feels like its in the muscle or on the right side of the breasbone right where my ribs connect) and sometimes on my left side, same kind of shallow ache, but it is higher up, kind of towards my shoulder.
The feelings of shakiness are commonplace with anxiety, they really are. And so is beng lightheaded, if you are really anxious, more blood is being circulated to your arms and legs, keeping you "ready to flee or fight". Less blood goes to your brain from this, which can cause some lightheadedness. Also, this explains why when you are racked with anxiety you cannot think well: Less bloodflow to the brain. It also explains the dizziness.
What are you eating? Do you avoid caffiene, sugar and other foods that can make you anxious?
I agree that it sounds like you are having panic attacks.
Lexapro is an SSRI antidepressant commonly used to treat anxiety and panic. While they are classed as an anti-depressant, they also have an affinity for treating panic and anxiety as well, hence why you were prescribed it. You were not Rx'd it for depression. ADs do not make things worse, for the vast majority of people, they are extremely helpful.
My recommendation to you is to get back to your doctor and discuss the anxiety issues with him. You may need to go back on something like Lexapro to help you get these symptoms under control. Therapy is also a must, whether you take meds or not. Therapy will help you learn coping mechanisms, and understand anxiety better, so you will be better equipped to handle it when it pops up.
Whatever you do, don't do nothing. There's too much help out there for anyone to suffer needlessly. Anxiety can be well managed with the proper professional help. I was diagnosed with panic disorder at 18, and was actually housebound for a while a few times in my life. I had panic attacks so debilitating that walking to the mailbox was hard. A combination of meds and therapy gave me my life back.
Please let us know how you're doing.