Someone is following me

I walk to the take transport, bus and MRT TO MRT and walk to the work place. One evening, as I was early I walked in white sands shopping centre. I was in white sand, at the front area I had to stop because the front was people standing and not moving. I felt someone walked into me, I looked back, there was no one. One morning, while walking out after passing the tickets tapping counters, there was again someone I front. I had to turn to my right and again some walked into me. I looked to my back but there wasn't anyone.