Hi love, it's so hard having bowel and stomach problems as it really never seems to resolve itself.  I have had many of the same worries over the years and like you been told it's many different things, IBS, colitis, stress and so on.  So in the end I kept a diary of what I ate and drank and anything that made me worse I took out of my food plan to give my tummy a chance to recover.  So we move forward many, many years as I am now the grand old age of 72 years and I'm still here!  If it was me I would ask to see a lady doctor, specifically about this, write down your problems, tell her what other doctors have said and don't go off plan.. A doctor will only concentrate on one problem at a time so make sure it's about your tummy issues.  You're still very young and stressing about this can cause you more problems.  If I am constipated I take a dulcolax capsule to help me then you won't be straining and pushing which can cause the blood and mucous.  I'm not a GP but I'm just saying how I cope, I also do deep breathing exercises to calm me down and drink lots of water,  so ring that doctor and get some help.  Good luck, Carol x