"I’m bisexual and a lot/all of my really close supportive friends (who are also apart of the LGBTQ+ community) keep invalidating my sexuality kind of by saying “your just gay come on, you know it” in like a joking manner because I’ve only dated one guy and he’s really been my only male crush in the past 3 years but it’s honestly making me doubt my bisexuality even though I am attracted to both male and female people and I guess I’m wondering how I can deal with it."
Sadly, your situation is common for bisexuals. It is an experience we go through both within the LGBTQ community and when living among straight people.
I am sorry to hear you have to go through that but be reassured your bisexual family is always here for you, and it is a pretty huge family (though often hidden and invisible to the eye...because we are magical creatures, =p).
I am surprised there are no bi/pan people in your group of friends. We are the largest part of the LGBTQ community. I'm guessing some of them might not know they are bi/pan yet (some of us only realize it later on because of all the pressure put upon us to be either straight or gay), or some of them might be hiding because of those same remarks you are receiving. There probably are many bisexuals among those who are perceived as straight around you as well.
In every group, the members of that group often try to rally others to their cause. It reassures them to know other people are like them, to form a bigger group. Even if it means erasing another person's identity. It is the same among us queers.
I know I have been guilty of this myself, labeling someone as bi when they were really gay because I perceived them as bi or because I really wished they were bi. But in the end, this is truly selfish.
You being bi doesn't make you any less a member of the LGBTQ community than your friends. That's what they need to understand. We're all in this together. Being united is key. You might be bi, but you're still fighting for the same cause and you are just like them.
No matter what their feelings are, no matter how much they may want you to be gay, they need to understand that what they are saying is hurting you.
Have you tried explaining to them how painful it is to you?
It is the same as when someone tells them "Have you tried being straight?" or "Why can't you make the effort to be straight?" or "Don't worry, I'll find someone who can help and fix you."
You do not need fixing. You are perfect as you are. Your level of attraction to various genders doesn't change the fact that you're bi. You could like other genders much more than your own and still be bi. Or you can love your gender more than other genders and be bi. You could spend your entire life dating your own gender and still be bi.
I have only ever dated men, and I can guarantee you I am very much bi.
It is not for other people to control your tastes. Not even you can control them.
If you haven't done it yet, I guess I would start by telling them how it makes you feel when they say that. The thing is to calmly make them understand that it is hurting you the same way homophobia or whatever kind of prejudice they're going through is hurting them. You can start by writing your thoughts down if it can help you process them more clearly to express them.
Being a bisexual comes with a lot of doubts. After 15 years of knowing I am bi, I still go through doubt periodically. I also go through periods of not liking myself.
Take care of yourself when that happens. You can listen to bi songs (Demi Lovato, Panic at the Disco!, etc...), read a bi book, watch bisexual Youtubers (my favorites are Courtney-Jay, Gaby Dunn, and Weird Norwegian), connect with other bisexuals to discuss how you feel.
Trust me, you will eventually find friends who are bisexual, either in person or online. And it always feels good to have someone to vent to who understands you. I've found that if there is one thing the bi community is good at, it's understanding each other.
Here is an interesting video about the bisexual spectrum that might help you. You will see a lot of these bisexuals feel more deeply attracted to their own gender than other genders.
I hope this helped. Don't hesitate to contact me again if you have other questions, encounter more issues, need someone to talk to, or for anything really.
Be strong! No one can tell us/control who we are even if a lot of people like doing so.
Thank you for trusting me with your concerns.