I (27M) keep doubting my fiancée (31F) after lies and broken boundaries — how can I know if she’s truly loyal and find peace?

I had a past experience where I planned to marry a girl but discovered she was cheating. That left me with serious trust issues that still follow me today.

Now I’m with a new girl (31F), and we’re planning to get married. She went back to her home country for a year. At the beginning, I trusted her fully. Later, I found out she was still talking with her ex “as friends.” I was about to leave her over it, but she apologized, accepted my boundaries, and said it wouldn’t happen again.

Then another issue happened: she told me she was at home, but Instagram location showed she was somewhere else. When I confronted her, she said she was visiting relatives and was going to tell me. She apologized again.

Since then, I’ve lost almost all trust. A part of me believes she’s loyal, but another part thinks she’s hiding something — maybe even cheating (I’m not sure). I’m also supporting her financially, which adds pressure.

Emotionally, things feel one-sided. I need reassurance to feel secure. She’s cold with love words, doesn’t talk about our future unless I bring it up, and some days our conversations are only “how are you.” When I tell her this bothers me, she says she’s “not in the mood.”

All of this is making me mentally exhausted. My brain keeps spinning with doubts, and I can’t focus at work anymore.

TL;DR: I (27M) want to marry my fiancée (31F), but she has lied before and broken boundaries. I’m constantly anxious and doubting her loyalty. Part of me thinks she’s faithful, part of me thinks she’s not, and I can’t find peace.

Final question: How can I know if she is truly loyal — and how do I find peace when my mind won’t stop worrying?