IB and periods?

Subhashini
Hi everyone , can someone help me with differentiating IB and normal periods? I usually have periods for 5 days but this time it stopped in 3 days also had medium bleeding where as I always have heavy bleeding, I tested on my second day of period and it came negative. Should I wait a little longer ? Or is this my light period?
Also my bleeding was brown in color and also I didn't had any clots which I usually have. Has anyone got periods and still got positive test ?