What is this thumping feeling!?!?

I have been TTC & I'm really hoping this month is my month (fingers crossed) But according to Glow I'm 3 weeks and 1 day pregnant (AF expected in 9 days). This morning I woke up with very sore BBS! & for about 3 minutes I felt like this thumping feeling in my lower left abdomen. It felt veryyy weird! A few minutes later I got a sharp pain in my lower left abdomen. Has anyone experienced this & got a BFP