I managed to feel the flutters relatively early, around 18 weeks. As long as there is cardiac activity at every gynae visit and no unusual symptoms (like spotting and etc), it should be fine. But if you are worried, please contact your gynae.
really depends on a lot of factors. some moms only feel after 31 weeks. as long as all vitals are good you may just have placement issues.
as long as on your every check up heart rate and ultrasound is fine.
rare for me too