Chris Henry's fiancee says the Cincinnati Bengals star "jumped" from the truck she was driving ... but he wasn't trying to kill himself.

Loleini Tonga opened up to ESPN. She said, "I think he thought maybe he was gonna land ... he was gonna land right? He wouldn't want to be gone away from his kids."

When asked why she didn't just stop the car, she said, "I was gonna stop, but there was nowhere to stop on that road."

I have to be honest..I'm having a hard time believing this lady!! I don't think he was commiting suicide, BUT I also don't believe she was innocent!