Emergency appointments are best if you feel able to keep yourself safe for a short while, but still need to see someone soon. You can search for your GP's details by postcode on the NHS Choices website.
if you are under 19, you can call: 0800 1111
Childline is free and open 24 hours. You can also email them and access their '1-2-1 counsellor chat' via the website: www.childline.org.uk
Sheffield Suicide Support
You can search for specific Sheffield support if you or someone you know is feeling suicidal here: https://sheffieldsuicidesupport.co.uk/