What Causes Severe Abdominal Pain?

hi doc,
question is for my wife as her last period was on 24 mar and the period has not come till today. she had tubal prgnancy last time ie on dec 09. she is experiencing abdominal pain from last week but not continuos pain. intermitant pain that does not last long. but had a bit severe pain a few days back. she is experincing burping of gas also.i would like to know that is there a chance of pregnancy or a case of another tubal prenancy as i had read that abdomal pain is a symptom of tubal.please advise us as a bit worried because one tube has been removed last time.pls also tell us what are the very early signs of nornal preg and also of tubal.