Cramping at 3 weeks 6 days

I am currently cramping at 3 weeks 6 days, period is due today. No bleeding or spotting but I have had a pretty bad cramp in my right side. I have read all horror stories about what it can be but I am looking for some positive peace of mind if it is quite normal. I know what to look put for and the signs of the worst outcome I need some positive reassurance if you have any. I have taken some tylenol and so far it has eased up but I have stressed myself out terrified of the worst. If it has happened to you, how long did it last for?