Hello doc now recently I have been having awful problems

Hello doc now recently I have been having awful problems with pooing. Let me give you some info on Saturday morning I woke up feeling very ill with a stomach ache and a head ache I was also sick twice I was fine on Sunday but now on Monday I can't physically poo and when I do I just see mucus and when I have felt what is in my bum it does not feel like poo one bit. The last time I had a poo was on Saturday night so I beg you respond ASAP because I am very worried about this bear in mind though over the past few days I have hardly eaten anything.
Your sincerely Harry Difelice