My partner is questioning gender

So my partner and I have been dating a little less than a year officially but we've know each other for almost 10 and been romantically involved for about 5 now. Last year he (we still use those pronouns) told me that he had questioned his gender or wasn't sure and I encouraged him to see a therapist to help him figure it out. It was all good. I'm very accepting and I love him for him not for his gender. My love has never been a question but lately I've struggled with some changes we've made. Like we no longer have hetero-normative sex and it's almost like he just isn't ready to admit that he is actually at the very least gender fluid if not trans. The unknown is starting to frustrate me. I'm trying to be positive and supportive of any changes he needs but it's all very overwhelming at times.  
Does anyone have any advice on helping someone through this or on relationships while figuring this out? We are both committed to this relationship.