A lady who has been experiencing normal menstruation
knows the difference between implantation
bleeding and menstruation bleeding.
Implantation bleedind is generally light pink and consists of spotting or few drops,while a menstrual bleeding is heavy with flow.
The way you are describing your flow seems to be a menstrual bleeding however just wait for few days and the confirm it with the help of the pregnancy
If it is a menstrual bleed,then obviously it means that IUI has failed.
Nothing to get depressed as you can again try for it if it has actually failed.