It sounds like you really do need to create a balance - if you're not quite content with how your D/s relationship is working. Explain to him clearly about your insecurities, and maybe take the level of your bdsm play back a few steps to decide what you're really happy with. Safe-words are to be taken seriously, if you find yourself using it and taking it back, be more clear in deciding what you can handle and what is off limits. I think it seems like you need to be told how great you are, what a good slave you are - more regularly. I assume he knows you were sexually abused, explain how your self esteem can be low and that harsh words hurt. If you're truely afraid sometimes of what you'll have to face if you speak, rework things out. If it thrills you, then fine - but fear can drive you into a corner, careful!