@Josi,
From what you've said so far, I gather:
- You are a biological guy who is very slight in stature, short and slim.
- You are not certain of your gender identity, but you currently tend to dress as a girl or unisex.
- Physically, you can pass either way. You may see yourself as "curvy", but from my earlier post, you aren't really outside male normal and I think you could pass as a small but otherwise normal guy if you choose to. Likewise, you are small enough that you could pass as female and it seems you are currently doing so.
- While you say you really aren't sure which way you want to go, it really looks to me like you have a preference, but maybe other people don't accept that and that is causing you issues. Is that the case?
From this, I have two inputs. First, while there are some people here who have been a bit rough on you, there are a number of regulars here who are willing to give you input, but you need to be a little more forthcoming. What's really going on with you? Second, are you asking us why you are this way? If so, biology is a wild thing and humans span a large range. Whatever your situation, it is the way you are. There is no doubt that lives are easier or harder because of biology, but you are who you are and there is no need to be ashamed of it. Figure out who you want to be and then chart a path to get there.
You also mention medical testing. How is your relationship with your parents going? Are they supporting you in this or is there some friction? Who is driving the medical attention?