Actually, some highly sensitive tests can detect it 4 days before your period. But for accurate results, it's always best to wait for the missed period day.
Implantation usually happens 6 to 12 days after ovulation, so testing before that won't show anything. Even my doctor said testing after a missed period is most reliable.
My gynac at the clinic suggested doing a beta hCG blood test for early confirmation instead of stressing over faint lines at home. You can call your hospital and ask.