Your LMP 22 April
You have bleeding following Unwanted 72 on 20 May. It lasts for 4 days.
You should expect your next period around 20 June.
Chances of implantation bleeding are not there because ;
a) You had sexual intimacy on 12 May, that was 20 days after the period. The time of Ovulation was 4 days earlier. So Pregnancy can't occur.
b) Implantation bleeding is just spotting, not 4 days bleeding.
c) You should do a urine
pregnancy test around 25 June if you don't get your periods by 20 June.