Sac seen but negative pregnancy test

February I had an ectopic I had my tube removed etc Iv still been having pain so today I went for a scan to see if they could see anything wrong with while I have pain but they seen in my Uterus an empty sac have done pregnancy test but they are saying negative Iv had blood test that are also negative I still feel pregnant, surly if a sac is seen but negative urine test doesn’t seem normal to me has this happened to anyone else? I’m also had a lot of pain today period pain but not to bad now had some bleeding but just like a light period please help