Pain can be excruciating from an Anal Fissure or tear.
Mucous should be there,but sometimes people with IBS or other bowel problems can get this.
Because you are so anxious I think you are missing the point some other posters have mentioned.
Bright Red blood is from something close to the opening,such as a tear or a pile.Sometimes Piles are internal,so cant be seen,and if they arent "playing up" when you get examined you may miss them,as when they are sore,and swollen you can feel them.
Bowel cancer signs are "changes" in Bowel habits ie. constipation or diarrhoea,though again these can be signs of other problems.
Dark Red Blood Stained Stools.
Unexplained weight loss etc. to name a few..
It sounds like you have irritated your Tummy with the Anti-inflammatories,either by taking them on an empty stomach,or sometimes they just upset you,anyway.
If you have been constipated,you can "tear" slightly straining,and this would cause spots of blood,or sometimes "splashes" of blood in the toilet,or straining can cause a "Pile",(or Childbirth)possibly the Stomach pain,and the blood is not connected,but just a coincidence.