Cramps but BFP?

Did anybody get real bad period cramps and/or lower back pain when af was due and for a few days after (I’m 3 days late) and still get a BFP?

I’ve heard of implantation cramping but I’m not sure whether you would get cramps when af was actually due/after. & also if they would just be mild cramps or feel the same? As mine are really painful.

Thanks ladies