chest pain and strange periods?.......

Hi
Never use these forums before but am just after some advice. If anybody has experienced this before or has any idea what it could be or what i should do i'd be grateful of a reply.

I havent had a proper period for the last three to four months due to me being underweight. Ive been seeing a therapist gained some weight and a period started last tuesday. I have been in agony and noticed that there are quite a few clots. Every hour or so i am dying for the toilet and have to sit there for 10 - 20 minutes due to the amount of blood i am losing. Originally i thought this may be down to the fact havent had a proper period for a while.
This afternoon though i feel really warm and sick, have actually vommited once and have really bad chest pain. My chest feels really tight and all my neck and shoulder area feels quite numb and strange.
If anyone has any clue what this could be i would really appreciate it.
Many Thanks