My stomach is full of stretch marks, and if I touch them with a little pressure I can feel lots of tiny bumps, no pain. What are these?

Tears in collagen. Stretch marks are damaged collagen amd in very wide thin stretch marks it can feel like little bumps. Treatment options include 1540 laser from palomar or carboxytgerapy, injections of medical heated carbon dioxide gas.
Collagen/scarring. When the 'belly' skin stretches quickly in late pregnancy the underlying supporting tissue can 'get damaged'. When the skin heals and tries to return to 'normal' tiny 'balls of collagen/scarring may be felt.