To cut the story short,
You had your last intercourse on 15 April.
You had Deviry for 5 days , finished on 1 May.
You did
beta HCG on 4 and 9 May. Both negative.
You had mild brown discharge from 11 May.
An intercourse on 15 April, if fruitful , will cause implantation by 24-25 April. So implantation bleeding can't occur on 11 May.
It could be delayed and minimal withdrawal bleeding due to Deviry.