I am most worried that I will never have a say in my own relationship. That it will always be overshadowed by what his partner wants. He fights for me when he knows that I need or want something, but the fact that he has to fight for it at all upsets me
Well, first of all, there really isn't anything we can control in life. We can discipline ourselves and keep our promises, but we can't control other people nor what life brings us.
That being said, you absolutely, 100%, without a doubt, have a say in your relationship! If you do not feel that you have a say, then why would you even be in that relationship? Take a look at what you are allowing to happen that is keeping you from having a say. It is up to you!
If you read these boards a bit, you will likely come across some references to the term "agency," which is basically the capacity each of us has to act independently and make our own free choices. You are your own free agent and no one limits you in our relationships unless you let them. Even married people have agency - a couple is made up of two individuals, after all.
The problem with many people new to poly is, they think that they are supposed to go along with crap they wouldn't normally put up with in mono relationships just because they think they don't have a right to question it nor expect anything different. People come here and say, "Is this allowed in poly?" as if there is some great rule book in the sky that decrees poly relationships must be a certain way and you better go along with it even if alarm bells are going off in your head and you know something isn't right. Ugh!
But, I ask again... do you feel
valued? Do you feel
respected? Do you feel your concerns are
heard and
acknowledged, or are they
dismissed? Are
promises made and
not kept? Is a third person not involved with you dictating terms for how you can be in your relationship? For most solos (unattached polyfolk), that is
unacceptable! Why should his relationship with her be treated as more important than his relationship with you? Love relationships are no place to have second-class citizens. That is not very loving.
If you were in a monogamous relationship with this guy, and he had a sister, would you let his sister determine what you can and cannot do with him? I doubt it! Just because he is married and poly, why allow his wife to call the shots for what you can and cannot do with him? It's only acceptable if that is something you feel perfectly comfortable with - but it is obvious you are not. If they have terms for how things can go, so should you! Develop your own boundaries, state what they are, and tell them what is negotiable and non-negotiable. If, for example, you don't feel comfortable going to his place for a date, don't. Have him over to your place.
If you can't be in a relationship with someone who isn't "allowed" to have an overnight (or rather, allowing his wife to dictate the terms) at your place, then step back from your involvement and say you won't accept that. Wanting to wake up with a lover is a perfectly acceptable desire - no one wants to feel like a dirty secret or mistress because the guy is always leaving before the sun comes up, and you're lying there in sticky sheets thinking, "Well, that felt good, but this sucks."
It sounds like she is fearful, insecure, and has him by the balls - and he isn't fully comprehending that he can exercise his own agency and stand up for his relationship with you to progress naturally according to what the two of you need/want/desire. It's sad that he always has to battle with her for that - she's not his mommy. You've only been seeing him a short time, so of course you are still getting to know him, but seriously, if you express your needs and they are continually postponed or brushed off, why stay? When the scales are more often tipped towards unhappiness, dissatisfaction, and sadness than connection, fulfillment, and fun, something isn't working.
If you feel you do not have a voice in your own relationship, any relationship -- doesn't matter whether poly or mono -- it's up to you to speak up for yourself and make a choice about whether or not you will continue to put up with bullshit. If he can't give you the basics you want, and the dynamic has you all tied up in knots and feeling shitty, this relationship is probably not for you. You can't just sit around and hope that this guy you're seeing goes begging for his wife to toss some crumbs your way, when what you really want (and totally deserve) in a relationship is a four-course meal.