Help where to start. New user. Never claimed.

Hi
I've just signed up and this is my first post. (Sorry if the post is long). The site is huge and I'm looking for help where to start. I've never required financial help and never looked into help from the state before. However, I've been informed the conditions I have and the job I have may allow me to receive some form of payments from Employment Support, Universal Credit and/or PIP.  
I'm a 49-year-old self-employed taxi driver who suffers from IBS-D, Coeliac disease, and Gilberts Syndrome. IBS-D is getting worse and I'm working and earning less than previous years. 
I was diagnosed with IBS-D around 25 years ago (Gilbert Syndrome around 35 years ago, and Coeliac Disease within the last 18 months). I take 8 Loperamide tablets per day for IBS-D.
My working hours have been reduced by around 20% per week. The stress, anxiety of leaving home to work at present has got quite bad; this is bringing on depression on certain days although I haven't received any medication for this. 
I've had numerous tests carried out in the last 2 years including endoscopes. Gilberts Syndrome along with IBS-D can produce abdominal pain, fatigue, loss of appetite along with a lack of concentration. I had 2 anal fissures operations around 10 years ago too which obviously hasn't helped.  I believe I am getting small panic attacks (within the last 3 years) when I'm somewhere where I feel uncomfortable. eg: too many people or lack of a toilet close by. I feel completely deflated, annoyed and depressed that I'm extremely likely to continue having major problems with this for the rest of my life.  This can obviously have a negative effect on life in general although my wife, children and family are very supportive.
I have now read that extreme cases of IBS whereby the person can prove the effects of IBS are "painful, disruptive, and distracting enough to keep you from working a full-time job", can apply for Personal Independence Payment, Employment Support and Universal Credit.  I understand I must have a health condition or disability where difficulties in daily living or getting around for 3 months are problematic and also expect these conditions to continue for 9 months. I was totally unaware I could apply for this help. I am suffering on a near daily basis with the conditions I have. I also believe my tinnitus which started in January of this year has been brought on with the stress of my conditions and is another added mental daily problem I know will never leave me. I genuinely can't see things improving as I understand I've now tried all suggestions given to me by Doctors and don't feel I've got many options left. Monetary factor will obviously help reduce stress at present and would appreciate any help and advice.
Thank you

Much appreciated. That gives me a good idea where to begin. Thanks very much.