Possible 2nd pregnancy

I had sex about less than 5 days before fertile window then the last day of my fertile window and day after... I had our daughter last year in Oct so I'm wondering is it too soon or "easier" to get pregnant less than a year postpartum... I been feeling crampy on my lower back area for a few days now & extreme fatigue.. can't go by my boobs b/c I breastfed.. Just want some opinions..

Ps: tested too soon a few days ago when I first got cramps got a Bfn but I know myself it was too soon.. and I usually don't get cramps before AF it's usually the first two days after it comes on not prior 🙁