First of all,

Secondly, SI is serious. It may not be a disorder in and of itself but it's symptomatic of much greater distress. The fact that you were so callously dismissed is downright negligent not to mention typical of the UK's current system.

I fully encourage you to continue talking about the issue - eventually someone will recognise that a service must be provided for you. In the mean time, focus on self soothing and distraction as much as you find helpful. Sometimes those methods too can be triggering but even if it delays any action on your part - that's a step in the right direction. Stay strong, we're here for you.