If you feel like you might attempt suicide, or may have seriously harmed yourself, you need urgent medical help. Please:
Call 999 for an ambulance
Go straight to A&E, if you can
Or call your local crisis team, if you have their number (e.g. from having been referred to them in the past).
If you can't do this by yourself, ask someone to help you. Mental health emergencies are serious. You're not wasting anyone's time.