No, you're definitely not the only one to feel that they can't accurately convey how bad it can get and how your symptoms affect your life!
Here are some things that I've found can help:
1) Keep a diary of your symptoms.
There are lots of different ways to do this but things you might like to include are no. of BMs, whether they're urgent or anything of note about the BM like blood, mucus etc., pain - levels and duration, also what were you able to manage with that level of pain? Or not manage? Can you walk? Move about the house? Sit up? Sleep - does pain keep you awake? Are you awoken by the urge to have a BM? How many times a night? How often do you get nauseous? If/when you vomit, and what you are able to manage to eat.
I think seeing the details of what you live with set out clearly like that can help someone who wasn't there with you (i.e. your consultant!) understand what you have been experiencing.
When I've kept a diary like this I've also found it helpful to rate my days Good, Bad or Inbetween. Then when you look back over a month it can tell you a lot about the overall picture - for example if you stop having many good days maybe you need to review treatment, or if you fewer bad days maybe that new treatment is beneficial.
2) Use examples to illustrate the extent to which your symptoms affect you. For example, "I was in too much pain to...." or "I didn't have the energy to...."
I think this makes more of an impression that just saying that you were in pain or tired.
3) Find a doctor who listens. Because with some doctors it doesn't matter how good you are at explaining exactly what you're experiencing - they just aren't listening! I literally have sat in front of a doctor, about 2 feet away, telling him how unwell I felt and how things were getting worse, while he appeared to be looking at my notes and nodding and when I stopped talking he looked straight at me, and said "Good. Well, fine then, I'll see you in 3 months".
Some doctors do not pay enough attention to what their patients say and with IBD finding a doctor that you can talk to really matters.
If you feel like your doctor isn't listening to you, I think getting recommendations from other patients, perhaps on this forum, can be very beneficial.