Caregiver Confession

I've been in a unique dynamic with my partner for about six months now. I'm a grad student at a local university and have been taking care of my partner, who has some health challenges that require assistance with daily living tasks. We never use the 'Daddy/Mommy' labels, but it's clear to me that there's an underlying power exchange dynamic in our relationship. At first, I thought I was just being a supportive friend and roommate. But as we got more involved, he started requesting help with things like dressing and bathing. It felt weird at first, but the more I did it for him, the more comfortable I became, and the more he seemed to crave that level of care. One day, he surprised me by asking if he could call me 'Mom' when we're together in private. The way he looked up at me with those pleading eyes made my heart melt. It's been a real emotional journey for both of us. He says it helps him feel safe and cared for; I enjoy the sense of responsibility, like being an older sister or maybe a parent. I have to confess something that happened last week though: we were in our designated playroom, yes, we set one up!, where he has this teddy bear collection from his childhood. We had just finished playing out a care scenario and he was lying on the floor looking so small and vulnerable. I couldn't help myself; I started to tickle him mercilessly. At first, it felt playful and fun, but then he said something that caught me off guard. He called for 'Mommy' in this soft, needy voice as he tried to escape my relentless tickling. It was such a contrast to his usual strong demeanor, seeing him so carefree and vulnerable really flipped some switch inside of me. I felt powerful yet protective all at once. He laughed and pleaded for mercy, but there was also something else behind it; it made the moment feel incredibly intimate. This is the part where I start questioning myself: Is what we're doing okay? We both agreed on everything beforehand and make sure to communicate openly about boundaries and feelings. But then again, tickling someone like that while they're so vulnerable... it felt wrong in a way, yet right at the same time. Am I crossing lines I shouldn't be crossing? I'm not asking for advice here; more like getting these thoughts out of my head before they drive me crazy. I guess what I’m trying to understand is if there’s something unhealthy about feeling this powerful over someone who trusts me so much.