You really didn't specify when your b/f broke up with you what he actually meant when he said he wants to work stuff out in the future but to me it sounds like he is basically wanting you to be a friend with benefits. I guess if I were you since he said he just wanted to be friends and if you feel he is even worthy of that then don't have sex with him.

I am sure you care for him however if the situation is causing you major anxiety it might be time to settle things with him once and for all so you can move on with your life. Have a talk with him and tell him how you feel and let him know that his behavior is not acceptable and it is not solving the problem nor giving you any closure. You can't change his behavior but you do have the power to change yours.

Life is much too short to be feeling anxious and miserable all of the time so now might be a good time to let him know that you need to move on with your life and he will have to sort out his issues and perhaps if he does and you are availabe and want to try again to have a relationship then it can be worked on at that time. For now though you should give yourself some time to meet other people and focus on other things as I really think if you do that things will become a whole lot clearer and you will start to feel much better. Let him know he can't keep texting you or calling you and most of all no more sex as that certainly will not solve any problems and he will continue to use you to his benefit. Hoping you can find the strength to stay away from him for awhile so things can get better. Best of luck to you.