Not sure how to proceed?!?

 First post ever, I am lost and could use some direction.  I(38m) have been married for 16 years, to my wife(37).  Before getting married I expressed a desire I had that I wanted to explore sexually, before committing to marriage. She assured me that she shared the same desire and that she was bi, and interested in sharing our bed with another lady.  We are now 16 years down the road, still haven’t come close to experiencing this.  I have checked off all of her wants and desires; she has a house, kids, career she loves, and I do absolutely anything she wants to do.  I have given up a lot of my lifestyle pursuits and changed a lot of the way I live, to better fit her lifestyle.  
 Now I have broached the topic and tried many times to bring up these desires and fantasies of mine.  Every time it seems that it causes personal injury to her when I do.  I ask if this isn’t what she wants any more and I am told it still is… yet when I bring it up or suggest we start a mutual dating profile, it becomes a fight and I am a bad guy all of the sudden. 
 I have been explicit and stated that I only want her to participate in things she wants, and I never want her to do anything she doesn’t want to do.  Consent is sexy to me, and it won’t be fun unless everyone is having a good time!!  However, she assures me she is interested still, but after 16 years of hearing this and seeing how her actions do not align, when should I come to terms with the fact she is just lying to keep me on the line?!?!?  Idk if I am overreacting or if I am seeing the writing in the wall.?.?.?

*I continue to try to explore the situation with her, as she becomes more comfortable…

 …or…

*I come to terms with the fact she is not interested, and I go down the path of those who are…

Your insight and advice is greatly appreciated, thank you in advance!!