Is anyone experiencing the same ?

My period is on 14 last month I didn't got mine till now .i did pregnancy test with first response it came not pregnant so I thought I am not pregnant but till now I didn't get but this whole week I feel so much pain n my back and stomach .Normally when I get periods I don't feel any pain anywhere but I dono why this whole week I am feeling pain and feeling bloated that too stomach alone .Did anyone experienced the same before if so why it's happening?