Being a supportive partner

Hey all! I've been with my partner for about seven months now and they started using they/them pronouns and a different name very early in our relationship (a little less than a month or so in). Obviously, I am very supportive of them and extremely happy they are comfortable enough with me and in their life in general to be true to themselves. Over the past couple days they've expressed to me that they are now ready to come out to their parents and are wanting to start HRT and practicing vocal feminization. At this point, I have grown to care deeply for my partner and will always support them as long as they are striving for happiness and health. I am so happy that they've come to this decision because I know they've been struggling with their identity for years, but I am honestly a little scared. I'm not scared of them, simply just that I don't know how this might change our relationship or if it even will. I'm scared of the unknown. I care about them SO much it hurts. I know my feelings are valid because we are both in this relationship, but I feel horrible for having them. It feels like I'm not being a supportive partner because of this fear of the unknown. I know they know I will always be supportive of them and I know they will always be supportive of me, but this is something I've never had to deal with before. Sorry for the long post...any advice or even just encouragement is much appreciated. I just want to be the best partner for them 💙💜