Good idea or bad idea? (Added a few paragraphs to answer questions in the comments)

I posted awhile ago about my SO being in the military and how in Janurarys drill he stayed at his “friends” house but his ex was up there and there was a receipt in his bag with her name on it from a hotel. Now. I came to ask his ex about it. But I know she will not be truthful to me, but she won’t tell me the truth either. I feel like she will maybe either protect him either way, or try to break us up if I message and talk to her myself. So my friend and I was talking about her texting her something about her hearing those two did something and was gonna tell her its Just wrong. To find out whether something happened or didn’t. And what did happen. I’m honestly scared to know the truth.. what it breaks me somehow? But what if I’m relieved to find out nothing bad happened. I just don’t want to live the rest of my life not knowing whether we stay together or not. I just want to know. Would you do it? Why or why not? Is it a good or bad idea? Please.. help. We’ve been together 8 months tomorrow (Valentine’s Day) But they were together 6 years and were married. Please not rude comments. Just be truthful on what you think of the plan. Thank you in advance!😭

Added:

The receipt was dated for when he was supposed to be at his friends. I asked to ask his friend and he told me no. We barely talked to me the whole time he was there. But I was okay with it bc I thought he was with his friend.

His stories don’t add up, so I thought about asking her without him knowing an see what she says. She may be truthful if it’s not me she’s talking to. I just wanna know what is said.

When we did have a discussion about it when I saw the receipt, he like didn’t care. And since then he’s been pushing me away. So I really don’t know how to feel. I’ve done talked to him about it. So I kinda just want to figure it out this way now instead.