Ive been with my partner for 4 and a half years. I love her with all my heart and would do anything for her. However one of the biggest issues in our relationship is she says I'm selfish.
I completely admit that I am and have been since I was young. I used to go out of my way to help people and do things for others but I keep being used and getting hurt for it, so I shut out other people and became quite selfish.
While I have managed to work on it a little, I am still far to focused on myself. I will often put my own needs and wants above my partners even without meaning to. I have trouble thinking of my partner first or even at all on the odd occasion when I could have done something nice for her.
She constantly brings me home little things and what not to show her love, while I am typicly a big gesture kind of guy I admit there is much more I could be doing.
How do I break this habbit for good so that if I am out I can think "hey bet she would like that" or do things for her forsaking what I may want?

To break one habit start another,until it becomes an unconscious act.

Example,set the alarm on your phone to call or text your partner just to say 'hello',

Again,set yourself a reminder to buy flowers or a takeaway,just so she does not have to cook.

I know this sounds like a odd thing to do,giving yourself reminders to show your partner you love her,but,when you are stuck in a bad cycle or habit,its easier to replace it with another habit then change straight away.

The changes will come gradually when your are more consciously aware of your actions,before you were unconsciously selfish,you did not realise what you were doing,now that your aware,you can make the changes.

Another nice thing to do is 'ask about her day' and listen to what she says,give her your full attention.

Finding balance in your life is not an overnight process,much the same as being selfish.It is a learned skill(balance)or defect in character(selfishness)

Balance with selfishness and the opposite,selfLESSness, giving too little,giving too much.

Developing these skills are a life long process.Many don't even acknowledge that they HAVE a ' defect ' like you are describing,they simply live life without thinking anything is wrong,passing by many opportunities because they are oblivious to the obvious(that others see)

To what extreme you choose every day, do you also do the opposite to ' make up ' for those days you went too far?

Food for thought.