Ectopic Pregnancy?

Help! I had an ultrasound done at 5 weeks and they couldn’t see any gestational sac. So I was ordered a blood test and my levels are 2,500 at 5w2d. I read somewhere that if levels are over 2,000 and no gestational sac was found on ultrasound that it is more than likely an ectopic pregnancy. 😓 i do have another blood test on Friday to make sure my levels are doubling and then scheduling another ultrasound in two weeks. I have had some sharp cramping but seems to be more related to gas/constipation and is on both sides. Only symptoms I seem to have right now are moody, emotional, frequent urination, cramping. Did anybody else gave good levels at 5weeks but did not see a gestational sac and if not be an ectopic?