Please help-Not Sleeping

I'm in a terrible mess. Not a minutes sleep last night. I get 3 nights a week like this. Everytime I try to go to sleep, I feel these very strange palpitations. Then I have to rush to toilet with dihayrria(sorry about spelling) and feel sick.

Try to calm myself down but everything starts again and Im just lying there for hours and hours.

My doctor insists theres nothing wrong with my heart but I think there is. I have had testes in the past which were all normal so I suppose he is basing it on them.
He will not prescribe sleeping tablets.

I just dread tonight.
What can I do?