I have ulcerative colitis which caused my B12 deficiency and resulting nerve damage. I too have pain in my lower abdomen which will be lifelong as whatever gets damaged won't heal. It causes pain in my left hip and colon pain as well especially when sitting down heavily.

If you have been checked as you say then don't worry too much about it but if you have bleeding it means a new inflamation has arisen and you will need antibiotics or steroids prescribed by a doctor.

I have been in remission since 2008 thankfully with no new flare ups but taking b12 is lifelong as well as iron supplements to avoid anemias. from what I have pieced together I started to get sick in 2003 and within 5 years became very sick.

It has amazed me as to how fragile the human body is yet how resilient it is as well. I have regained most of my nerve damage done but have some mild nueropathy in my arms, hands, and feet. Muscle calve twitching etc. My doctor told me that whatever has not healed after 2 years more than likely won't. Thankfully I have regained almost all of what was damaged.

The colon pain I attribute to nerve damage but it may just be a result of the UC. My lower instestine on the left feels very painful when my bladder is full like i really have to go pee it puts pressure on the injured part of my large intestine.

be wary of B12 deficiency if you have IBD because it is fairly common. Nobody knows what causes UC or other IBDs but most diseases it seems are autoimmune in nature and really have not much of an answer for a cure.

Good luck and pay attention to your body, I had several almost meaningless symptoms I either attributed to old age or being normal and they were not. It wasn't until I felt tingling on the left side of my face and my hands felt like they were vibrating as well as not being able to feel my feet did I know something was very wrong. I also have white circles of light in dark rooms when i move my eyeys back and forth from nerve damage. All of the symptoms i had/have are the same as MS but we found what was causing it and I see a doctor once a year for bloodwork and a checkup.

Pay attention to everything. Mucous or blood in your stools is not normal and you need to make sure you recognize that stuff when it happens and don't put it off.

This being said I am physically active, riding bikes and playing ice hockey and baseball and take care of myself so you do the same.