The only thing that means you're pregnant is a positive pregnancy test. You can't rely on diagnosing yourself, because people who miscarry, quit birth control, switch birth control, or are trying to conceive will have these same symptoms.
If you think there is a chance, test! You can test up to four days before you miss your first period. And always assume you may be if it will affect your decision to smoke, drink, get an x-ray test, etc. Better safe than sorry!