Hi Dan, I had the same thing at 16 weeks. I had cramps (and I never had real cramps before, just the twinges). I think it was also because I was overdoing things. I also had alot of twinges and lightning bolt sensations iykwim. I saw my GP and he said at this stage the uterus is pushing up which may cause some discomfort and pains. He said not to worry unless I was doubled over with pain and/or had spotting. I know it's worriesome, I panicked too. Get checked out at your GP for peace of mind.