Hi Natzer, stop what you're doing right now! Breathe in through the nose, slowly through the mouth, do that about a baker's dozen times. Relax!
If you're that worried talk to you GP or PD next time you're in. Otherwise, here's some info....
4 months old is when most babies finally acquire their sleep patterns and just like us, the way older ones, we have deep sleep, usually for adults those are around 3am.
My two were finished with the night feedings at around the 4 months mark, and yes there would be periods of their sleep when the were like dead to the world, so do we, unless the little tyke is NOT breathing then there is no need to panick.
A suggestion that might help, don't shoot the messenger, first get rid of all the surveillance, if your little bundle is healthy then quit those... Secondly, something I did myself, I was living in a two floor place when had my first baby. Had requested a moses basket (I think that's the name for them, still available in Tesco Direct and Argos) from friends. Finally got one myself, and had it with me where I spend most of my day, the living room.
Also, had to admit I had the very best help at home during those first months, you'll laugh, my chihuahua puppy, yes you've read correctly, she got in the basket with my girl, slept on her feet to keep her warm and comfy, and if I wasn't in the room, she let me know when my little munchkin was waking up.
Take care, chill, things will be get better with time. SMILE!
CD