my heart is acting very strange?!

I am 21 years old and healthy. Except for one thing that I find troubling. Starting since I was around 14 or so my heart would start to beat funny. Like it was fluttering. This would only happen once every 6 months or so and symptoms would increase more frequently. Well I am having my first episode of the year and it is the most intense. Here is what is going on: It started a last night a few hours before bedtime. My heart would beat randomly. No real rhythm that I could detect. Then it would start beating a normal beat and kinda slow but really HARD at a normal pace. Then I could also feel it beating normal and then every third beat or so i could literally moving. Like back and forth. I can feel it hitting against my left lung. And sometimes it would be hard one beat and really light the next. Sometimes the hard beat is so hard it literally shakes my torso like i just jerked my body. I would experience all of these different heart rhythms in about 3 minutes. It lasted for a few hours last night and I decided it was because I was drinking too much caffeine and it would be back to normal in the morning. I also developed a mild headache. Well when I woke up it was all still the same (but no headache). All I have drank today was water and one bottle of Gatorade hoping it really was caffeine causing this and it would soon go away to no avail. I developed another headache as well today. AND I have been experienceing a very weird and kinda painful left jugular. I have no idea what this is and why it is so bad this time. I am getting worried but I do not want to go to the doctor about it in case it is nothing. Also, this has happened through out my life but never this long or intense. Every other time I would schedule an appt with my dr it ended up going away before seeing him so there was no way for him to really know what is going on with me. I have not really had much of an appetite lately and have been feeling very fatigued because of this. Also I have just experienced mild diarrhea. When I take a deep breath I can feel my heart beating hard against both lungs. Anyone else experience this? If so, what is going on??