Do I believe my therapist or my gut?

It's safe to say that you've given your therapist far more details on your past and current relationship that you've dropped here. We literally shouldn't even try to answer your question on how little you've told us.

From this immediate perspective? Trust your therapist. She or he has a greater bigger picture understanding than we ... and possibly you (due to emotional bias).

You should use your brain, particularly the rational part of your brain. Ask yourself honestly if this relationship is making your life better and allowing you to grow as a person. The question is whether you would be better off without him.

You should never trust your gut. Guts are irrational and driven by emotions. Guts are very often wrong, that is why we have brains.

You should listen carefully to what you therapist is saying, that is why you have a therapist, and therapists can help you cut through the emotional noise, but ultimately the decision is yours.

Use your brain.

Glad you're seeing a therapist about this.
https://able2know.org/topic/497162-1#post-6793621

I would agree with 'ucertinaty400.' What you wrote does not equate to years of therapy and reflection . . So the guy lied to you about money. Odds are he has lied to you about many things and is lying to you now.
If you wish to give him the benefit of the doubt - DON'T!
There are many books out there about trust, how to establish it within a relationship. It is something that must be discussed and agreed upon between both parties.
I've been through this business before. I'm going through it now. And, it's not enough to take someone' word for it. Trust is earned. It's a transparency between two people. Truly, it is not a guessing game.

Your "gut" is your brain. It's certainly not your stomach or intestines.

"Gut instinct" has served humans for hundreds of thousands of years. Obviously not always accurate but in an environment where a mistake means extermination, pretty effective.

Not necessarily relevant to the OP, but your conceit concerning the human brain is foolish

The word "gut" implies an feeling that does not involve rational conscious thought. I wasn't really making a comment on physiology. I was saying that making important decisions based on emotions is often a bad thing.

My point was that when it comes to important life decisions, you should be using rational conscious thought informed by input from thoughtful people who don't have as much emotional involvement.