Not understanding the definition of "flutters" when it comes to fetal movement

I'll be 21 weeks along tomorrow, first time Mom. I haven't felt any actual kicks yet. I'm not sure if I'm understanding my baby's activity clearly. So far, when I close my eyes and touch my belly to focus sense on the baby, I'd feel like a "pulse" like a heartbeat around the area of my belly button either below it, to the left of it if laying on my left side or sometimes feel like a weight sitting in my abdomen when sitting still. I went to the hospital a couple days ago for chest pain, they checked the baby's heartbeat and it sounded very loud. As of today, I felt the pulse sensation but further away and not as strongly. I know the articles say don't wait on it. How do I know if I'm even sensing my baby?