How do I ask my husband for khula, when the problem is with me?

Assalamulaikum, I have been married to my husband for almost 7 years, we got married in Pakistan and live in the UK. Despite having a pretty normal and supportive relationship, with all its highs and lows, we still haven't been able to consummate our marriage. This is mainly due to psychosomatic condition that I have, and unfortunately my husband is suffering because of me as well. I sometimes think that we haven't been able to consummate this marriage because I might not want to have children with him, when he desperately wants them. I have suggested that we adopt a child, but he doesn't want that either. I have suggested several times to him that we part our ways in a friendly and civilised manner, so that he can get married to someone who wants the same as him and he can consummate his marriage, as I feel that he shouldn't be suffering because of me. I want him to be happy, and have children of his own, which I know , wouldn't be possible with me. I have tried medical/ psychological/ physical therapies for years, but nothings seems to work for me. My husband has made it clear that he doesn't want to leave me or re-married, but I feel guilty for bad for him to be in a sex less marriage. I think it would be the best thing for him and me to leave me. I feel that if after all these years, I still haven't got better with him, maybe we just aren't meant to be. Furthermore, as we are progressing in our marriage, he is getting me more involved in the family politics (we are also cousins) which is scaring me and having a bad effect on our relationship, as well as the relationship with my parents and siblings. Most arguments and conversations are now about this, rather than us a couple, which I am getting sick of. I think it would be best if we part our ways but how do I go about this? Jazakallah khair for reading.