To me, it sounds like anxiety
. I have had it for years, and I remember feeling just like you are now. That is the first thing I would try. A simple anti anxiety pill should help a lot. Usually even a general doctor can prescribe something like that. Or he/she may suggest you see a therapist. Mine has helped me so much and I don't feel like that anymore.
Another thing is, you may want to ask your doctor if you have a murmur. I have one, and it has made me tired, given me heart palpitations, and stuff like that. I had an echocardiogram
, and it was determined that my murmur was the common kind, and that it would go away by itself, or not, but it wasn't dangerous. They can also be treated by a simple pill if they are there.
At 23, you are probably not facing anything too serious. So I would go to my regular doctor, and just explain how you are feeling and take it from there. You don't have to feel like you are feeling right now. There is help out there!
I wish you the best!