What Causes Vaginal Bleeding Between Periods?

I am 25 years old & sexually active being married for 1 year & we have used condoms. I have always being normal on my periods every 28 day & it last 7 days. Is the first time this happen to me, I just had my period start on June 18 and finish June 25 now on July 8th two weeks after the period is over, i had gone to the restroom & notice bright red bleeding but not spotting it only happen one time then nothing for the next 2 days now on the 3rd day it happen again is that normal? my regular period is supposed to be on July 16th. Thanks