You cannot feel it stopped growing immediately.But u will find some symptoms,such as your breast is not tender than before.You find you have some brown discharge<---but this could be safe if not continuous,then red discharge coming out...of course later on bleeding....When u feel this, the fetus has been stopped growing for over a week,maybe more than two weeks already.
What I suggest is you must see a doctor and check with ultrasound more often to see the situation.
We are not the doctor, out feeling is not accurate if compare to the ultrasound scan. Don't wait for check up if you feel curious. Spend $400 to private doctor to check is safe.