Should I keep trying?

I have been married to my partner for 7 years, but we have been together for 12 years total. When we were dating, my partner did all the right things that made me fall in love with him. He would spend quality time with me, talk to me on the phone every day, put effort into holidays/anniversaries, and plan various events/buy random gifts to express his love for me. Over the past five-ish years, it seems he has completely stopped doing the things that made me fall in love with him (random love letters, late nights of talking about random topics, nightly phone calls when he's out of town for work, playing board games together). He hasn't acknowledged or planned anything for valentines day or our anniversary the past few years, rarely talks to me when he's at home, and doesn't do the little things I love anymore. I have expressed my frustration and my feeling of lack of emotional support/connection to him lately, and he has in fact acknowledge that his effort has decreased, but nothing changed after we have these conversations. After a while of expressing my frustrations with no changes, my feelings for him started to decline (maybe 2 years ago?). I even told him this and it felt like he wasn't taking me seriously until I told him I was considering divorce if we continued on the path that we are on.

On top of my feelings for him declining, I feel like my feelings for someone else have gotten stronger. There is guy I used to hang out with in high school and we were sexually active, but never anything serious relationship-wise. However, he was an amazing lover and probably provided me the best sexual pleasure in my life. We recently started talking and have been talking almost every day. I feel as if I am emotionally connected to him, and it makes me upset that I don't feel this same connection with my current partner. Also, my current partner does not provide me sexual pleasure, and because of my lack of emotional connection with him, any sexual encounters that we have make me feel super uncomfortable, and sometimes I cry at the end. I usually engage with my partner sexually because I feel like I owe him. I have not orgasmed from my partner in the 12 years we have been together, as I was hoping that our sexual experiences would improve as we became more intimate over the years. Although I have been talking to this old friend often, I do not want to leave my partner FOR him. He just reminds me of what I feel like I should be getting from my husband, emotionally and sexually.

My partner and I have gone to couples therapy, and have gone to multiple therapists over the past year, but so far I have seen little change in our interactions and my feelings towards him. We will try certain exercises and recommendations from the therapist, but rarely are they consistent. I feel as if I am initiating most things to keep them consistent, and if it is not me initiating these things, then they won't happen. My fear is that my feelings have not changed because I am still maintaining a friendship with my old classmate who fills the emotional void that I have with my husband. But I also wonder if I just need to give myself more time to see if my feelings change for my partner.

Do I keep trying with couples therapy and other things to focus on strengthening my marriage, or should I just go with my gut and consider divorce? My partner is a nice guy, but overall I feel unhappy with him, and I fear that my feelings for him just won't change.