Needs some more history about onset and progression.Palpitations and racing heart can be physical manifestations of severe anxiety. It is very important to evaluate medical causes. Some tests are required. If everything comes well you need to treat the condition after consulting psychiatrist.

Yes stress can cause delay in periods. Also you are showing symptoms of anxiety. Please consult psychiatrist and take medication for your symptoms.

Dear you, Yes stress can delay period. But incase you are worried about unwanted pregnancy.  Get yourself tested. And if that is not the case. To break the cycle of fight and flight mode. Step1- morning sunlight and tea. Everyday for minimum 10days. Your vagel nerve will get better. It detacts temperature change and brings your body in present moment. Step 2- cold water bath before bed.  Do it. Your body needs to come back in present. And don't wait for this phase to magically disappear. Just do the above 2 steps first. Then figure out what caused this. Calm the water before you want to see the surface. You will be fine. Don't worry.