What do women's aid do? I'm sorry if that's a stupid question.
Not stupid at all.
If you call their mainline, you can tell them all about the problem & they can give you the details of domestic abuse agencies in your area.
They can give you support, tell you what to do & how to stay safe. They will help to find a counsellor who is trained in domestic abuse - which I really think you need - they will be able to help you through this time of your ex trying to get back in contact. Please tell them about your self harm, it's very common in women who've been abused, and they will be able to help you with that.
There is a 'Survivors Handbook' on their website, which you download & read. Which will help you understand what is & has been going on.
Also I suggest onto the thread on this forum called Support for those in Emotionally Abusive Relationships and talk to the women there. There are many people who have been in your situation.
At the beginning of that thread there is a list of information/books/websites on abuse - I suggest you read all of that.
Women here always recommend this book by Lundy Bancroft called:
Why Does He Do That?
You might also look at this website:
Freedom Programme
You briefly mentioned abuse in your past prior to this relationship, when you were very young.
If that was sexual abuse - then I suggest you call Rape Crisis. You can talk to the helpline about what has happened in your life. They will give you an appointment to talk to a counsellor trained in sex abuse. If you look on their website they have a whole section on sexual abuse.
Their Freephone helpline is: 0808 802 9999
What you're going through & have been in the past, is so hard, you really need to call as much help & support around you as you can now. The support is there, you need to go & ask for it.