Recognising and accepting that you are treating your partner or ex-partner abusively is the first step to stopping the abuse.
Respect is an organisation which seeks to end domestic abuse by supporting those who are being abusive to change their behaviour. They provide several resources on their website which may be useful and you can access further support through their helpline (0808 8024040) web chat or by emailing them at info@respectphoneline.org.uk.