Tina,
During a rough time in my life (about ten years ago) I was on Zoloft for two years. During that time, I had a lot of palps. Not sure if it's due to that, because I still get them, but I had a lot more of them then. Zoloft is for depression, but I didn't know that at the time. I had anxiety, not depression, and my doctor finally realized that the Zoloft was making my anxiety worse (caused me to feel shaky and actually have hand tremors.) I was switched to clonazepam at bedtime, which is a lot like valium, and works better for anxiety. Addictive, but I take only a small amount.
Well besides stopping smoking I'd say discuss with your doctor.
A rest HR of 73 is good, but I don't know what you mean by "hard heart beat"... but your description of it keeping you awake makes it problematic.
If you have no pains or other symptoms you should be fine, and need only to figure out a way to deal with the loss of sleep. Is it possible that the hard HB is at least in part psychological? You mention zoloff, is that a depression drug? I've heard of it but draw a blank at the moment, so I'm just guessing.