I'm a 17 year old transmale and I've identified as male for about 2 years now. I am 100% confident that I am a boy, but I am also fine having breasts and a vagina. I don't think of them as female. They're just my parts! I like wearing things like dresses and skirts as well and I enjoy makeup, none of these things make me less of a boy in my eyes. However, I fear that people will not take my identity seriously because of this. Even in the LGBTQ community, I feel like people will say I'm not "really trans." Dressing the way I want to really boosts my self-esteem (and I have struggled with horrible self esteem my whole life, so I really need it) but being called "girl" and "she" really hurts. I guess my question is, how do I deal with wanting to present a certain way but hating how it makes others perceive me? I will be going off to college in a few days as well, and I know that could be a time to show how I really want to be, but I'm scared of how people will react or treat me.
I'm going to make probably the biggest understatement of the year: gender is complicated.
As obvious a statement as that is, it's still true, and I think it's worth repeating.
I think one thing a lot of people - even many gender-savvy folks or fellow trans people - sometimes forget is that there are a lot of components to gender and that knowing someone's gender identity doesn't provide much information about what their gender expression or presentation will be. Plenty of people, whether cisgender or transgender, have gender identities and expressions that don't fit neatly into a rigid and binary system of gender norms.
There's not much you can do, ultimately, to control how others react to your gender presentation. Expressing your authentically-gendered self, whoever that is and however you present that at any given time, might mean that some people might question or disrespect your gender identity, but those reactions are outside of your control.
Trying to manage the way other people interpret your gender presentation is only possible to a very limited extent - I can't tell you how many times in my past I've gone outside feeling really excited about my gender presentation, only to have the majority of people I encounter read something completely different in what they saw. People are diverse and complicated and they bring their own backgrounds and experiences to the table; you can't know what gender cues any one person will pick up on.
You certainly could choose to present as less feminine in some situations if you feel like it's a tradeoff you want to make for safety or comfort reasons; you might feel a little less comfortable with your presentation, but it could also help you feel a little more at ease in a new situation. The only way to really gauge what feels like the right balance of inner and outer security is just to test it out, I think.
You may find that over time you get a pretty good sense of what you're comfortable with in different situations and contexts. Many people have variations in self-expression based on circumstance - even the most binarily-gendered cis person will probably rely on different dress and behavioral cues at, say, a formal party with new co-workers than they will at a casual dinner with lifelong friends - and it isn't selling out or being inauthentic to tweak your presentation to some extent based on who you're with and how much you want to share with them.
In terms of people not taking your identity seriously, or arguing with you about whether you're "really" trans or not, it's certainly possible that some folks might have that reaction, sadly.
If people you care about cite your presentation or mannerisms as some kind of proof that you aren't performing gender to their specifications, sometimes it can help to gently (and, when necessary, less-gently) call them on it: do they have any non-gender-normative habits? Does that make them less of a man or a woman? Do they think cis men who wear skirts aren't "really" men, also? I tend to give people the benefit of the doubt if they are confused by some aspect of my gender expression, but after I've explained myself to someone or corrected their language once, I don't think it's my job to keep explaining myself to them and waiting for them to respect me.
I don't want to make light of the stress that this might cause you at all, but I do think that there's an upside here: being your authentic self with people, and asking them to respect your gender identity, means that it'll be really obvious which people don't get it and don't have an interest in trying.
It may be frustrating, especially at first, but if you can get comfortable asking people to use the right language (or whatever else you need from them), it often gets easier with time and can serve as a great way to learn which people in your life are really willing to make an effort to be good to you. If you can get a good core of supportive friends, their support can make it easier to handle people in your life who are less respectful, and might help you feel less upset if you wind up becoming less close to them as a result of their actions.
It is true that some people, even in the LGBTQ community (and even, sadly, other trans folks!) can be pretty judgmental about how other people choose to express their gender, or any other aspect of their personality. And while many colleges specifically have groups on campus for queer folks & allies, the trans-friendliness of those groups can vary from college to college. I would definitely encourage you to seek out student groups on campus; those could be the official LGBTQAETC group, queer-friendly or queer-focused activist groups, or other groups related to interests you have - there are certainly going to be fantastic gender-friendly people in groups other than explicitly queer ones.
Another resource you might find helpful is Genderfork, which has a lot of pictures and experiences from a wide range of genderqueer, genderfluid, and trans* people. Sometimes it can be helpful just to see that there other people out there forging their own gender-expression path, especially off the usual, known or expected trails.