Hello~It sounds like you may be having PVC's or PAC's ( Premature ventricular contractions or Premature atrial contractions)both are usually benign and we all have them. They can definitely feel like your tummy is dropping. As to the dizziness, that can be brought on by fear, I have had all this, it is not fun, but I am still alive and I am now 62. I would try not to worry too much about them, I know they are scary and it is difficult not to worry, I am the queen of worry. If they continue or get worse, then, for your own peace of mind, I suggest seeing your GP and telling him/her about this, they may be able to put your mind more at ease.
Dizziness can be brought on by fear but I wouldn’t necessarily shrug it off as that quite yet... especially if accompanied by dry mouth or any other symptoms that tend to occur after syncopal events.
I would definitely go see a GP or go straight to cardiology if this is an option for you without a referral.
Any family history of heart problems or sudden death?
Any other potential fainting or near fainting episodes you can think of?
Do you exercise or play sports? How do you respond to absolute peak exercise? Have you ever felt these palpitations at PEAK exertion (ie during exercise NOT immediately after; when heart palpitations are normal to find)?
What feeling came first: the drop of the dizziness?
I would recommend cardiology to obtain a type of heart monitor called a “holter monitor” to take home and wear for 24 hours to as long as 2 weeks.
Personally I tend to be more of a fan with longer monitoring, even though it’s more expensive and labor intensive to read.