Don't want to have sex with Fiance even though she's overall a great partner and beautiful. What to do boys?

Throwaway ACC for obvi reasons.

For context, we've been together for 7 years. I'm 32M she's 29F

She's beautiful, intelligent, caring. I know we can have a great future and family together.

Our sex life is not great and as a result I am worried that I will end up cheating on her in the future and ruining everything. I care for her and would not want to turn her world upside down in a couple of years, with a potential kid in the mix. Should I continue to block things out and pretend everything is fine, or exit, or try to help her change?

My main issue is that she as a person just doesn't seem to be very sexual. She doesn't like flirting, sexting etc. she also doesn't enjoy penetrative sex. We've had a few talks about this over the years, and over time I found out that she could go without sex for years and that she's just never been that interested with anyone. She also mentioned that the main reason she has sex is to satisfy the other person and to feel closer.

I have always found this challenging... My guess is that most people don't like having sex with someone who is not really enjoying it physically... Myself included. We've gotten to the point where she initiates the vast majority of times and I just end up coming up with excuses not to do it(...not great, I know).

I'll basically only end up agreeing to it or initiating after I've reached a point where my hormones take over and I just need to get it out of my system (like every couple of weeks)... Which I don't think is the way it should be.

I've tried introducing toys, talking about it etc. I make sure to make her orgasm before we even penetrate every time (otherwise the sex is too painful for her)... But none of it has made a difference and we've kind of agreed that "it's just how she is and always was".

I've now reached a point where I came super close to cheating on her and I don't know if I'll be able to resist the next time something similar happens. I know I wanted to go through with it.

A close female friend recommended sex therapy or giving it one more try to spark her sexuality.

I'm not sure if either of those will work. I'm also worried that they might work for a while and then revert back to normal. I feel guilty for taking up 7 years of her life, I don't want her to spend another couple of years with me... Only to find out that I've cheated and that she needs to find a new partner when she's older and potentially with a child.

So, should I break up now or try to fix things or continue suppressing myself?