Lovers to friends?

I [28F] been with my partner [31M] for 10 years, ever since I was just 18 years old. When I met him I wasn’t looking for a life partner at all, I hadn’t even figured out my sexuality yet. I remember distinctly that I wasn’t sure I was attracted to him when we met, but he seemed like such a good guy and I did want to get to know him better. Before I knew it I was years into the relationship. We’ve been through so much together and the love runs very deep. However, I did always struggle with a lot of what if-questions. A few years ago I finally admitted to myself (and him) I’m attracted to women. I started calling myself bisexual, but I did wonder at many times if I was attracted to men at all. At this point my partner and I did not really have sex anymore. I started wondering if I really enjoyed the sex in our earlier years because I felt attracted to him, or because it felt new and exciting as I had never been with anyone else before.

Fast forward to a couple of months ago. We decided to open up our relationship. My partner has been right by my side during all those years of questioning myself and I tell him everything, so he wanted to stay by my side while I go explore who I am and what I want (he however, does not feel the need to explore this with other people). I decided to not date, kiss or go to bed with people who don’t know I’m in a relationship, as I don’t want any drama. So I’ve been very upfront about it and have gone on multiple successful but casual dates with both women and men. I was shocked with myself how easy it was to have sex with other people. I had great fun and it felt a lot more natural than I thought it would after being with the same person for 10 years. So it wasn’t the act of seeing other people that I found hard and confusing, it was telling my partner about it, as we decided it was important to communicate very openly. I knew I wasn’t doing anything that wasn’t allowed, but I was still afraid of hurting him.

This brings me to my very confused current state. I realised that at 28 years old, I still have no idea who I am or what I want/like. I have not been an adult for a single day without my partner by my side and I’m curious to find out who I am outside of the relationship. But at the same time I love my partner so immensely, I’ve been crying for weeks at the thought of losing him. Two things can be at true at the same time. I love that man so so so much and I adore what we’ve built together over all those years. I cannot picture a life without him. But I’ve also had the uncontrollable urge to explore what life is like without him (not just sexually speaking) and I know those feelings won’t go away.

I would absolutely love to find a way to not lose him completely, but still create space for myself to rediscover myself. But that feels very selfish and also impossible.

Random facts and things that make the matter even more complicated:
– He moved country to be with me when I accepted a job offer abroad about 6 years ago
– We bought a house together last year and can’t resell it for another 2 years
– We’ve only had sex about 5 times in the last 3 years
– We don’t sleep in de same bed anymore
– He was oddly very okay with me telling him about my sexual adventures with other people, it even surprised himself
– Last year we talked about marriage a lot but even though we didn’t doubt if we wanted to be in each other’s lives forever, we could not find a way of marriage that felt right for us
– He still insists he does not share the need to be with other people

Is it possible that my partner and I are really more like best friends who tell each other everything and support each other no matter what? But then how do we go to comfortably being each other’s friend if we’ve only ever labeled it as a romantic partnership? And what if I’m the only one seeing it like this? I don’t want to string him along or hurt him.

tl;dr: Been with my partner 10 years, since I was 18. I wasn’t sure I was attracted to him at first, but he’s a wonderful person and our bond grew deep. Over time I questioned my sexuality, came out as bi, and we eventually stopped having sex. We opened the relationship so I could explore. He’s supportive but doesn’t feel the need to explore himself. I’ve dated and had sex with others (both men and women), and it felt surprisingly natural and fun.

Now I’m 28 and realizing I’ve never truly known myself outside this relationship. I love him deeply and can’t imagine life without him, but I also feel the urge to find out who I am on my own. We share a house, a long history, and real emotional intimacy, but I wonder if we’re more like best friends now. I don’t want to lose him, but I also don’t want to live dishonestly. How do you shift from a romantic partnership to a platonic one?