Hi everyone, I'm a 21 year old AMAB and I've been struggling with all of this stuff for a few years now and I'm still having a lot of problems.  I've basically been in the questioning phase for 3 years now and still don't really feel like I know where I lie on the gender spectrum.  I think I have basically accepted that I am at the very least not cisgender, but I don't know how to figure out anything beyond that. All of this is so very frightening to me.  I've started anti depressants a couple months ago and that has helped me a decent amount, but I had really been hoping the dysphoria would somehow go away as I took them though, which of course did not happen.  I have had anxiety issues since childhood and depression issues since puberty began, some OCD issues (mainly obsessions, which often makes me worry this whole transgender thing is all in my head), and more recently, since I really began to realize I could really be trans, issues with dissociation and depersonalization.   How can I be sure that I really am trans? How can I know whether it is just my OCD making me think I am, and if I and trans how can I figure out HOW trans I am?  It's so upsetting to think about and I just really wish I could be happy being the person who everybody sees me but it is becoming harder and harder to do that.  I am just so worried all the time.  My girlfriend and I have been together almost 5 years, and I've only somewhat recently told her about all these feelings.  She is pretty worried too. She is very much capable of being attracted to women but she worries if I transitioned that she wouldn't be able to feel an emotional/romantic attraction with me anymore. And I want to be with her more than anything in the whole world.  I had been getting ready to propose to her actually until I told her about all this stuff. Gah. I want to get married. I want to have kids, I want to start my career as a high school social studies teacher after I finish school, I want to have a dog and go camping with my family.  I've always thought I was going to be a father, but now every year I am more unhappy with my increasingly masculine qualities.  I am so worried all the time. I just want to have the life I had planned and I feel so guilty for feeling like I tricked my girlfriend into falling in love with a persona that really is not entirely me.  She loves me though and has said if I ever transitioned she would at least try to stay together and would if she was still attracted to me sexually and romantically. And that gives me some hope. But like, our relationship always had this steady anchor of feeling like no matter what we would always be together because we felt so much like we fit, and now there is just this sad anxiety about the relationship because what if I need to transition and then we break up.
I'm just quite upset lately.
I want to figure out if there is any way I could be happy if this really is gender dysphoria and I choose not to transition. I want to figure out if I can be happy if I do transition. I'm terrified to think of transitioning because maybe I would regret it after a couple of years and have permanent changes and stuff and lose my girlfriend and friends and maybe my dad.  I just hate burdening other people and feel so selfish thinking about transitioning. 
I work as a cashier at Lowe's and have to talk to all these super masculine dudes all day long every day.  And it is so hard because either I put on a masculine persona and they respect me (but I dissociate into another fvcking dimension), or I act more feminine and they don't listen to anything I say and I feel myself and them and my coworkers judging me.  I get home at the end of the day every day and am just so utterly exhausted because I have had to pretend all day.  It is agonizing. 
But I worry that if I transitioned I wouldn't get over any of this and I would still be just as unhappy as I am now, just without my girlfriend and etc.
I'm in therapy right now, but she is about to have a baby and will be gone for a long time so I'll have to start over with my issues with somebody else. I haven't really gotten that much closer to understanding myself since starting therapy either, but maybe that's just because she doesn't have that much experience with gender issues. Idk. Idk what I want from this post, maybe it is just to vent. I am sorry to put another one of these types of posts in here, but thank you for taking the time to read this if you did.

Fears? Worry? Predicting what others will think?

I would say join the club but you already did, welcome to Susan's.

You're not the first or last to have this flood your brain, and you have been thinking of this for many years. My advice is to breathe, seem a counsellor trained in gender identity to see which steps are appropriate and perhaps, when you're ready and are more grounded experiment. But before you come out or seek out HRT (unless you're already sure) I would implore you to seek a well trained counsellor who can give you the tools.

Of course it's in your head, your brain, like any trans, or gender fluid brain, is not wired the same way as a Cis person, but that doesn't mean it is any less real, it is all very much real.

As to the rest, please seek out a gender therapist, they will be able to help you figure out where you fall on the spectrum and if you are ready to move forward, or not. You would be surprised at how much this can affect your depression, I used to fight major boughts of depression before I started HRT, it's been 7 months since my I started and I haven't had any issue with depression.