One day you will realize you were a fool for wasting so much time on this girl. Many opportunities have probably passed you by. If you don't believe that, then you are probably going to be single until you are 40. Grow some balls and don't take someones shits. If you are jealous you cant be with her, then pretending your just friends is only screwing yourself over in the long run. You're getting used. Simple as that.
Grow some balls and be blunt with her. If she doesnt like what you have to say or how you actually feel, then theres 3.5 billion other women in the sea.
Ive been exactly in your shoes. You call the shots. Next time she needs something, just say no. The fact you have low self esteem just means she will never come back to you in the way you want. Girls never go for guys with pitty. They use them.
Current Stable: Some Audi with a V10, Couple of BMW's, one F Car, and one P car. One lonely GT-R with all the Euros.