There is a big, BIG difference, actually. There are different types of feminization, now that I think about it. Feminization can be something as superficially aesthetic as a man getting all dolled up and dressed like a woman for sex play stuff. Or it can be more than that, to the extent that they actually take on the role as a lifestyle. On a more medical note, it could be the long term process of taking hormones to actually change the body to take on more female characteristics.

Being submissive on the other hand, has absolutely nothing to do with gender roles. Men, women, straight, gay, etc. can all be submissive. Also, there is the difference of sexually submissive and socially submissive. Also, that is not to say that an individual would ALWAYS be submissive to every person they meet (sexually or socially). It's all very personal.

What do you mean exactly by 'not happy with your male parts'? Me, I wish I didn't have mine and had female parts instead.

Stuff can be really confusing. It was for me. I myself, had a long and introspective transitional time before I came out. The best advice I can give you here, is to try and not think about it in terms of straight or bisexual or gay or whatever. At least not just yet. Just be open and honest to yourself about what you want and why. Once you can answer those questions, you should have a more clear definition of where you stand. Sometimes people are just curious and as soon as the situation presents itself, it is totally wrong for them. Try not to associate one want that you have (preferring to look more feminine) to an assumption of what it could mean (you can't be straight). Think more on WHY do you want to look feminine? Why do you prefer a submissive stance? Because it makes you happy? Then, Why does it make you happy? etc., etc. Do this with different aspects of yourself.

Sort of, to an extent. What I see in you is where I once used to be. Although it was in a different context, I had reached a point in my life where I questioned who I was and was desperately seeking some kind of definition. I'm not saying you will wind up where I am, but you are at a crossroads that is not unfamiliar to me.
When it comes to my sexuality and my self perception I know exactly who, how, and why I am. (It wasn't easy to get here, btw). When it comes to how I show myself to the public, I have done all I can (or am able to do for the time being) to portray myself as I wish to be treated and accepted.
Like you, I also have a difficult time finding persons that are willing to take me seriously for who I am and what I want. Sometimes this makes me feel guilty or invalid. Regardless, I love how far I have come. I just wish it could be further.

And thank you for posting up in the first place. I know how frustrating it can be to be searching for a label when nothing seems to quite fit. I very often feel like I don't have a place in the world.
But sometimes I think that maybe no one has a place in the world, and the ones that pretend they do are just lying to themselves to feel better about it. <-- That's just my personal thoughts, though.