Low back pain but not pregnant

Hi, so me and my boyfriend dry humped on 12th November and I was wearing undies and he’s wearing undies and pants so it’s like impossible for me to be pregnant but I’m still worried. My period came on time and heavy on 18th of Nov till 22 of Nov. On 18th of Dec my period came to as heavy flow till 23th. But yesterday, I had low back pain and my legs were sore the whole night when I’m trying to sleep. So I’m wondering if anyone experienced this before and can someone confirm me that I’m not pregnant so I won’t be worried😭