Indian. Perhaps I'm asking this too late.

My (29) long-time LTR (28) (back from my ultra-beta days) dated in school until she moved to an elite uni in another state. Due to not finding a long-distance comfortable (she would do things I wasn't aware of, go for vacations in co-ed groups without my knowledge, etc), I decided to move on and fucked another girl after telling LTR I'm done. She took this as infidelity and swore to find "better than me".

Skip to 4 years after - her Chad 6'3 boyfriend has moved abroad, her mother has passed away, and she's back into my life. No particular reason why she's back with me except that she has realised I'm her true calling. I'm immature enough to take her back. She says she has made out with 1 guy and slept with 1 (Chad BF), in this period. I dig out her past, whatever I can, and I grow more and more uncomfortable with the situation. She says she was happy with her ex, they broke up as he moved abroad. He texts a couple times. She meets him once without my knowledge (claims it was just a "dinner").

The next 3 years: I try to break up but she apologizes, pleads for me not to leave as she would not be able to carry on with her life. Meanwhile things escalate towards marriage (our parents meet, etc.).

I try to break up multiple times, but never can gather enough balls to walk out on my incredibly hurting LTR. And given that everyone knows of us dating.

LTR has multiple green flags - financially well off, reasonably mature, pulls her weight in the house, cooks, does not ever deny sex, accepts she's a lil over weight and working on it. All-round a responsible, sweet 'lady', though with a long history of nagging me (but I accept my BP-ness).

At the same time, I can't help feel cucked given that LTR went about finding someone better, found them, got dumped (possibly?) and came back to me as her rebound.

I'm at a crossroad where it's singlehood or marriage with this LTR (India...).

Any advice appreciated.

About me: I'm doing financially pretty well (better than LTR), lift 6 times a week (reasonably good shape), decent with women - though this pain point dampens my spirits often as I find myself wondering wtf I'm doing with my life having second thoughts about my lady more often than I'd like.