How to get a diagnosis? So I've been having IBS symptoms for the last 10+ years, and I self diagnosed myself about 4 years ago. 
I have diarrhoea 90% of the time, with the other 10% being constipation. 
I am woken up in the night with stabbing stomach pains if I eat dinner, and my body rejects anything I consume until I've been awake 3+ hours or so, including liquids other than water. 
I can't eat when I'm not at home, or when there are other people at my house, as I can't handle the embarassment afterwards. 
I want to get diagnosed as I'm 20, and struggling to commit to working a full time job, as I'll be eating so rarely that it won't be healthy. 
How the heck do I even speak to a doctor about it though? Like I don't even know where to start, or what tests to request. 