I constantly worry that my son will die before me and he's only 3 mons old. How will I handle when he goes to school or drives or plays sports?

See a psychiatrist. Probably you will benefit from therapy to discover the reasons for you fears but medicine may help as well--i'd start with a professional who can evaluate your problem your family doc may help you find a good one.
Excessive worry. Excessive worry is a feature of generalized anxiety disorder. If this is causing problems for instance you repeatedly check to make sure child is breathing during sleep or cannot sleep because the thought goes round and round in your head all night or you have feeling of constant fear or dread then it needs to be treated with ssri prozac, celexa, zoloft (sertraline) etc. Otherwise counseling would be adequate.