I know from past experience that it is hard to hurt someone, even if they want you to. He has to find his confidence and learn your limits in a more physical way than just 'you telling him what you like'. There is a difference between knowing on an intellectual level that its ok to hurt someone you care for and actually being able to do it. That emotional block often kicks in.

I think you need to just keep going as you have been. Sounds like you are doing everything right - communication, care etc. If you try to force him to do more too quickly you may find you scare him away or change the dynamic of the relationship to the point where you are topping from the bottom.

A few suggestions:

- Maybe you could try to switch for a little? Its not essential for a Dom to have been a sub (as some I know have claimed and there is a lot of debate about this) at some point but I think doing so helps to give a better understanding of what certain BDSM activities feel like. You don't have to necessarily switch to the point where you are Dominating him but you could, for example, let him try things on himself with you helping so he can see what they feel like. That may help him realise that its not pain but pleasure for you.

- Make lots of encouraging noises while he is doing things and beg him for more in a 'please sir, may I have another' way.

- It may be worth you having a safeword if you don't already. You may not need it but if he knows you have one it may make him feel happier about doing things to you. If he does lots of things to you and you scream and cry etc he may feel that he is hurting you when he is not. However, if you have a safeword and he knows that this means you don't want him to stop unless you use it he will not stop even if you cry and scream. I know from personal experience that safewords can make a sub more confident about a session and I think it can also make an inexperienced Dom more confident.
- Suggest he combines the safeword with a level of physical pain that is adjustable. Start low and build and tell him that you will safeword when it is too much. Keep doing this and he will eventually learn your limit. As the person experiencing the pain you are not in a god position to know what you can and can't take as you are too close to it. As an impartial observer he can relate what he is doing to how you are reacting.
- I know some professional Mistresses offer a couples service where they oversee a session between a couple (usually a dominant woman and a sub man). They offer advice and help and supervise the session to make sure there is no danger etc. I am not aware of there being any professional Doms so you may not be able to do this but is there a Master you can trust to take you under their wing for a few sessions to help and advise him? Someone who can stand in the corner and supervise and make suggestions etc?
- Ona similar note, how involved are you both in the local scene? Do you go to play parties and munches? If not, maybe you should start to go as a couple. Leaving him alone with a few of the Doms while you sit elsewhere and talk to the subs will give him the chance to talk to others who may have experienced what he has experienced (and may still do so) and therefore have advise and help. Besides, peer support is a good thing in this case - he needs to know that what he is doing is not wierd or unusual and that others have the same feelings and desires and you both.