Lower back pain from the inside

Horrible, excruciating, pain. In my lower back. My menstrual is late, even later than normal. I have problems sitting over the last 3 days, pain has plateaued, for now. But its still horrible. My hips hurt as well, when I'm sitting. I've tried extra strength Tylenol and it barely did anything for me. Leading up to this I was having sudden stabbing pain in my lower abdomen. Already a mom of 2 boys. If this is a sign of early pregnancy, it's nothing I've ever experienced before. I can still poop, so I'm not constipated. And a hot shower only made my back pain worse yesterday. Anyone have any ideas? I could use some.

Side note- I have to wait til Friday to test, due to being broke. Lol. Bills I tell ya.