Ectopic Pregnancy

Can anyone who’s had an ectopic pregnancy please explain how it felt and what symptoms they had? I know that abdominal pain on one side is a common symptom but how does the pain actually feel? As of right now my period is late, however when I took a pregnancy test it was negative. Now I have sore breasts and pain on one side of my lower abdomen. The pain feels more like a bubble of gas...and when I sit down or apply any pressure to my bum I feel the discomfort