Although the nature of the superconducting state has been intensively studied in FeSe, many fundamental issues including the pairing symmetry and superconducting fluctuations are still highly controversial. Here, we report a revised $^{77}\mathrm{Se}$-nuclear magnetic resonance (NMR) study on the superconducting state of $^{77}\mathrm{Se}$-enriched bulk FeSe. Below the superconducting temperature (${T}_{c}$), by carefully avoiding the rf heating effect, a remarkable linewidth broadening and obvious reduction of the Knight shift are observed under external magnetic field along both in-plane and out-of-plane directions, suggesting an intrinsic superconducting nature. These exotic results unambiguously rule out the possibility of chiral $p$-wave pairing, and favor a pairing scenario with the mixing of ${s}^{\ifmmode\pm\else\textpm\fi{}}$ and $d$ wave. A slight decrease of the Knight shift well above ${T}_{c}$ is also revealed under a moderated external magnetic field, suggesting exotic superconducting fluctuations beyond phase fluctuations in the two-dimensional limit. These renewed NMR results provide valuable constraints for the theoretical models on the exotic superconductivity in FeSe.