If nothing living can’t be that small explain bacteria and phytoplankton and cells

Its true that bacteria, phytoplankton, and cells are all forms of life at a very small scale, it's worth noting that these entities are fundamentally different from a human fetus or a grown human being. They lack the complex structures and systems, such as a nervous system, required to experience consciousness or pain.

The comparison between a fetus at a very early stage and these microorganisms might be misleading. A human being is a multicellular organism with highly specialized cells forming complex tissues and organs.