While it is honorable to sacrifice for a marriage, and all marriages do require some kind of compromise and sacrifice, I believe the reason is you are being far too self sacrificing here... you have allowed the situation to completely destroy your agency. You should never feel compelled to get a false diagnosis just to keep the peace and in order to appease your in-laws, in order to cover for your husband. That does not help him confront his problems, and only enables him to continue. The more you sacrifice your own truth in this manner to prop up these illusions, the less you will be believed, and the less agency and authority you will have. You must stand up for yourself and for the truth.