Worried about my marriage.

So here is the issue I have a hard time being excited about sex with my wife I think it might be because she used to turn me down all the time, to a point where I was convinced that she didn't love me or was cheating on me or something it killed me on the inside. That situation only resolved after I made the choice to join the Army and before I left decided that I was ready to have a child. We started to have sex more often but now I feel like she only wants sex to have a child and could care less what I want/enjoy. I feel like our sex life is extremely one sided as we have been together for 8 years (married almost 3) she enjoys receiving oral sex but never gives it and has only ever given half hearted attempts in giving oral. She only ever wants to be on bottom and we nearly never do anything but missionary. She never initiates sex and will almost never touch my penis. Beyond all that she is worried that I am gay because I have admitted to being bisexual although I've explained it's strictly a sexual thing and I know that nothing would ever happen because I'm with her and she isn't into it. I've tried to get her to play with my backside with mixed results and I've said that I want a strap on because it excites me and I think it could be intimate for us. She just doesn't seem to care how I feel sexually I don't know what to do about it because when I bring it up she gets upset and acts like I'm "going after her" or trying to make her feel bad some goes for when I try to communicate how bad all this makes me feel she even told me that if she had known about my bisexual feelings that she wouldn't have married me. I don't expect anyone here to have a magic solution I just needed to vent because I'm hurt and scared.

People do change. The person I married is not the same person now, but then neither am I. As the vows say, 'for better or worse, in sickness and in health', etc.
Working on things together helps a lot. Asking for what the other spouse wants (on a personal level) helps. Sometimes when I ask for what I want, she just rolls her eyes.
I would never go outside the marriage for what I desire, but it has crossed my mind. She was left by her first husband who cheated before their first child was born and I would never want to hurt her. There is some anger, but it is mostly despair.
Feeling trapped is no good for either spouse in a marriage. Having children and finances intertwined with the marriage makes getting out of it not really an option for either of you.
It isn't easy. Do what you can to help. Counseling and lawyers are expensive. Church or 12-step groups are free and very helpful at getting back on track.
Seeing other happy couples shows that it can work. Finding out how can be learned. Remember that there are no rose gardens out there and a relationship is usually very hard work to maintain.
Best of luck to you both.

Try to get some colors in the marriage. Be romantic send your wife's favourite flowers. Write love words on the note. Make her feel get loved.