It sounds like it's time for you to move on.
This you must do. She is using you 100%. It is not a pleasant decision to make, but for your own pride, please end it asap.
because I love her so I find myself running after her like a puppy doiing her shopping, buying cigarettes etc and I feel so stupid.
You are in love with an ideal, but the reality just doesn't measure up. No-one, absolutely no-one, is worth that kind of hassle.
I understand how hard this is for you, a lot of us on here have been in similar positions. It is for the best.