It doesn't always mean they're split up. It depends on the other factors. I think the others have given you a good idea about your situation.
All four of my married parents (the fifth one is divorced) sleep in separate bedrooms. My dad and stepmom can't sleep together because my stepmom moves around too much and likes to watch TV in the middle of the night, but my dad is a light sleeper and needs more sleep than most people. My mom and stepdad can't sleep together because my stepdad apparently snores and kicks my mom too much, and also there's not enough room in the one bed for them and my little brother (who needs to start sleeping in his own bed). But they still kiss each other and say they love each other and do things together, and they say they're not split up, so they're not. It's just a practical solution that makes it easier for them to sleep.
Your parents seem different since you said they don't kiss and cuddle anymore, and you said they don't seem like a couple anymore.
If you're worried about your parents not loving each other, I've been there. It makes me sad sometimes that my parents can't all live in one big house with my brother and my pets and me, but I also have had good experiences that I wouldn't have had if my mom and dad had stayed together. I barely even remember what it was like when they were together because I was so little when they split up, though. Maybe it will be different for people who are used to their parents being together. I hope you don't have a hard time and I hope they don't fight too much.