Hey, everyone! Sorry I haven't managed to reply to you all individually. Clearly, we're a distressed bunch who really need some help.
I'm going to link some resources below:
It's important to first know a little bit about attachment theory (I learned about it whilst on my degree, as I have a degree in Psychosocial Studies):
www.psychologistworld.com/developmental/attachment-theory
In terms of understanding what attachment styles are and what anxious attachment is:
www.simplypsychology.org/mary-ainsworth.html
internal.psychology.illinois.edu/~rcfraley/attachment.htm
(very informal video but she explains it really well)
In terms of learning to overcome/manage anxious attachment:
As @Adventuritis pointed out, there's a book (also available as an audiobook on Audible, which is how I'm accessing it) which directly deals with this. It's called 'Insecure in Love: How Anxious Attachment Can Make You Feel Jealous, Needy and Worried and What You Can Do About It'. I'm only a little way in at it's really good so far:
www.amazon.co.uk/Insecure-Love-Anxious-Attachment-Jealous/dp/1608828158
I also believe that a large component of anxious attachment is negative core beliefs about one self (low self-esteem) - a sense of low worth/value, not being good enough etc - so I'm also trying to raise my self-esteem. There's an audiobook called 'The Six Pillars of Self-Esteem' available on Audible which someone has uploaded as a video on YouTube. It seems to be really good/quite life-changing, according to the comments:
There are lots of others, so have a look around using words like 'attachment theory', 'attachment styles', 'anxious attachment', 'preoccupied attachment'.
Also, here's a little video that I think represents me/my relationship (and I'm sure a lot of you/yours) to a T in relationships: