Please help! I have a period cycle of 28 days. My last period was on 13 March and I’m due on 10th April.

Having terrible on and off lower back cramping . Also I feel heaviness on the uterus and slight lower abdomen cramps. I have been having these pains since 28th March . Does it mean implantation pains? If not or yes how do I control the pains ?

Ps- I had unprotected sex and my husband did cum inside me on 23rd March when my risk of pregnancy was 9% high