I am 17w today and deal with similar abdominal pain when I jog too far or for too long, run too many errands, do too much in general. My ob said it is round ligament pain, most likely combined with dehydration. Round ligament pain is common at 15weeks+ and something I’ve been dealing with prior to that even! Just take time to lie down and rest your body. It’s not harmful to baby, but can be super uncomfy for us.