Ay, stomach cramps during pregnancy can be normal talaga, lalo na kung kasama lang ng dumumi, pero 16 weeks na kasi kayo so better to check with your OB just to be sure, mas comfortable ka lang of mind, lalo na pag ongoing pa ang cramping or may bleeding pa. One of my mum friends had the same worry at 16 weeks, and the doc said it was ligament stretching, pero she felt so relieved after the checkup talaga.