FTM I need answers

So I am currently 21 weeks today, work a 40 hour job, and full time student. I recently had two days off consecutively and I think I felt the baby moving.

How does it feel to actually know if it's the baby and not something else? There were certain times that I felt it was kicking or at least readjusting. I felt pressure like pain. Sometimes it didn't even hurt but others it did.

Since I'm always moving or on my feet at work it's hard to feel my baby moving. I just want to know if this is normal or not. Also jut started to actually feel the baby moving by the middle of week 20. Strong movements at least.