What are r chances

It says only 3℅ chance getting pregnant 10 days before my period start day. My SO had sex yesterday and all day today I have had cramps and extreme back pain. I know this is a little too early to be sure, in my first Pregnacy those were the signs I had knowing something was up. Just wondering if anyone else has had similar experiences? Or I cld just be over thinking this all and I'm just feeling this way because of great sex and my inevitable period lol 😒