I am sorry that you are struggling, but there are a number of "red flags" here in your short posts that could have indicated that this outcome was likely.
...I have feelings for her but she doesn't like me that way...
...she is limited on what she is okay with....mostly that it's ok for me to touch her but she is not interested in touching me.
This is it's own problem, and not really limited to poly.
Lopsided relationships are not healthy for anyone, yet you stayed in a sexual relationship for over a year with someone who a.) doesn't reciprocate your feelings and b.) doesn't want to touch you sexually?
If you were single and dating (or married but dating separately) would you have continued to date someone who didn't give you the affection and sexual attention to foster a real relationship? For over a year? It certainly sounds as though you "put up with" an unhealthy dynamic for the sake of "poly" so that you could be "dating" the same person as your husband - no wonder you are struggling!
...We are not publicly out about our relationship at all and she was never ok with me talking to anyone about it for fear we would get outed. She doesn't know I joined this forum. We are trying to all still stay friends but like....idk it's all a struggle. Is this gonna get easier?
I get not being "out" about your relationship (we are not publically out either), add in the fact that she is CHEATING, and of course she doesn't want anyone to know! But, as your friend, cutting you off from potential sources of support - even anonymous ones! - is NOT kind behavior, especially since she can NOT be that support person since she is part of the equation.
The fact that you feel that you have to hide the fact that you are posting on an anonymous forum? Definitely highlights an unhealthy dynamic here, to me. So, how good of a friend is this person to you, really? When she doesn't encourage you to get the support that you need? Healthy relationships (even friendships!) require honesty and communication - which does seem to be lacking here.
... Her husband is unaware of her affair with us.
Yeah. So. Dating cheaters is a good way to bring unnecessary conflict and drama into a relationship style that is predicated on honesty, communication, and informed consent of all involved...Many of us would advised against even dating someone who was ALSO dating a cheater, let alone dating a cheater yourself. (Lots of threads about this here on the Forum.)
My husband and I have discussed in depth what we want our next relationship to look like and it would have to involve a person who is equally attracted to both of us.
Long term we would love to find another woman who can be with both of us together or separately and build more of a life together on that. But only if it's the right person.
This underlying requirement is probably the biggest red flag pointing to the fact that this will be an ongoing struggle. "Equally attracted to both of us" is not practical, and perhaps impossible. People are different, we are attracted to people, or not, at different times for different reasons. Every single relationship grows at its own pace depending on the people involved and their experiences together. Each relationship needs the opportunity to foster intimacy for itself (one-on-one, not all-three-together)
There are reasons why they call this "unicorn hunting" (someone will probably post David Noble's link for me) - it's because unicorns don't actually exist and that "right person" you mentioned is not a real person that you will find, but an idealized version of someone who only exists in your mind.
*****
Bottom Line? - my recommendations:
1.) Don't date cheaters.
2.) Don't date co-workers
3.) If you date friends, realize that it may end the friendship!
4.) Your "best friend" is not a GOOD friend if you have to keep things from her and she allows herself to be in an unhealthy relationship with you in order to be with your husband.
5.) Date separately from your husband (Don't worry, I know that you will ignore this one, everyone always does

- but it is probably the biggest hurdle that you are facing! The absolutely Number One reason why most couples fail to successfully transition to poly

)
JaneQ