Maybe you should tell your husband about it. It is not clear whether the ex bf himself is the sole cause of the increase in hypomania, or, also, the situation you are creating by being clandestine with your husband exacerbates it. If you can tell the husband (most people would understand that the first bf - the one who got away - will always occupy a special place in your mind), you will eliminate the potentially exacerbating component of being clandestine, which might help.