Heart has been beating irregularly this past week

Hello everybody, This is my first time posting on this forum. I felt compelled to post because of the heart problem I have been dealing with this past week. I'm a 23 year old male that has an active lifestyle.

But, this past week anything remotely active has been so hard for me, from mowing the lawn, walking up stairs, or standing up. Anytime I do anything physical, I become lightheaded, breathe heavy or shortness of breath. I'm not sure what is really wrong with me, but I think it's my heart because I physically feel weak and my blood flow feels weak.

This all started last week, when I just woke up and walked up the stairs to my office room. Once I got to my room I fainted for a few seconds. Ever since that fall, I've been experiencing my symptoms 24/7. I can't do anything physical without feel lightheaded or out of breath. Even getting out of a car and standing up makes me dizzy. I cant even jog and mowing the lawn felt like the hardest workout.

Im not sure if my heart is the problem, I don't know what else it could be. But, anything that requires cardio has been so hard for me. I'm planning on seeing a Doctor soon. But, in the meantime, I just wanted some input from the community. Thank you everybody.