Stress can definitely bring on health anxiety. I myself have a fear of just keeling over if I do anything to exert myself (even house work).
You might want to try discussing it with your doctor. Other options would be to seek out a therapist that deals with anxiety disorders or even find a group therapy (a lot of them are free but not sure about where you live) where there are others in your situation who you can relate to and share ideas for coping.
Health anxiety seems to be the most common because it plays on our own fear of pain, suffering and death. When someone close to me is really ill or hurt, I sometimes have nightmares about myself dying.
You are not alone and you need never be. Seek out help. Hopefully your boy friend will be understanding. If you do choose therapy, ask him to go with you. He will be able to see what it is you are dealing with. Many times, significant others who do not have it, just do not understand until they hear it from a professional.
Best of luck and keep us posted!
Lindaru