@Jaila
I'm sorry to hear about you mum. It must have been such a shock and then to lose her so quickly. I've been dealing with cancer for a couple of years now so I know how hard it is on everyone, but losing her so quickly after the diagnosis must have been so terrible.
I remember when I first tried dating in my early 40s... yep, I did say I was bad at it... there were so many things I thought I should hide about myself because it would just reduce my chances too much I thought. Now I don't want to in any way compare what I felt any potential date wouldn't like about me to what it must be like as a trans person. I don't have any experience in that area at all, but I can see how it could be a big thing to tell someone if they're not aware. I honestly don't know how I would handle that if it was me having to make that decision. But I ended up going with as honest as I could for 2 reasons. To avoid an awkward conversation if things started going well, and if they agreed to meet me then they already knew those things about me. If it was a reason to not go out with me, then it was never going to work anyway I thoughts, so might as well save both of us that time.
As you say, it is a big part of who you are, and I can tell you're not trying to hide anything, but I also understand the hesitancy when you both seem to really get on well at the moment. But I just think it's one of those things that the longer it goes without you bringing it up, the harder it will get.
As for the how? That's difficult. I'm not being very helpful am I. I suppose you could just say there's something important you need to tell him about yourself and that you do trust him enough to tell him and that it isn't easy for you. Whatever you decide to do, I really hope it works out well for you. It does sound like to me that you know you want to tell him, but obviously don't want to risk what you have with him now. All I can think of to add, is that if he's what you see in him, then his response will at the very least be respectful to you, so trust him to be the type of man you feel that he is.