That sounds about right for the timing. I'd get a bleed about 3 days after I started the red (sugar) pills. When you stop the active pills, you get a withdrawal bleed. It doesn't really seem to matter if you've been taking the active pills for 3 weeks or 3 days.

The cramping may be due to stopping the pills "mid-cycle" (ie, not waiting until you were due to take the sugar pills to bring on the regular bleed)? I don't know since I never did that.

I think you're probably fine, but if it's worrying you, it's worth speaking to your Dr about it. They will know if there's anything they need to check out.