I had the same and it made me feel really concerned, as the baby can now hear you the advice I found on Interned is try singing to your baby to wake them up. Also, for me it is always a bit easier to feel the movements when my belly is full. I am not an expert but that helped me this week.
I had this but my baby decided they want to hide for 6 days. I called my midwife on day 4 and she said it was fairly normal as they are still so small and have probably moved to a location where you can’t feel them kicking. She said to phone up in a couple of days if I still felt nothing. I phoned yesterday (day 6) and went in for them to check the heart beat. All was good and baby started kicking again last night. I would suggest phoning your midwife if concerned they can then invite you in to check the heart beat to give you some peace of mind x
If concerned, call your maternity day unit however movements do get more frequent and stronger as you progress in the pregnancy especially if this is your first baby, it might not be regular until 24 weeks x