Almost fainted/ped out from laughing?! PLEASE HELP!!!?

I was having a video call with my friends tonight on msn and I was crying with laughter. I became really dizzy and my head felt heavy from laughing so much. I almost ped out on several occasions. I thought at first this was nothing to be weary of, but noticed it very severely today. I also have other conditions like tremors, heart palpations, severe anxiety, and burning sensations in the feet/legs. My doctor wont take me seriously, but I have never had an episode bad like this before. My body was swaying back and forth and I was disorientated. What is wrong? I went to a cardiologist last year and got a clean bill of health, as well as had a pulmonary function test and everything was fine. I am really scared and this is starting to ruin my life. Why should I be afraid to laugh???? I still feel very dizzy and feel like I am still going to p out, and it's been an hour.