worrywart
A person who worries excessively, especially about unimportant matters.
It doesn't mean you're a worrywart, a nervous wreck or in need of heavy medication.
Where it comes from
From worry + wart, apparently chosen for alliteration. Presumably related to earlier worryguts. Attested 1956, but earlier examples are found in newspapers of the 1930s and 1940s.
Adapted from the Wiktionary entry worrywart (CC BY-SA 4.0).