Is it wrong to have a FWB relationship with my ex husband?

We’ve been separated (not divorced, in my state we have to be separated for a year before you can file for divorce) for a few months. We still talk daily like we’re friends and we’ve had sex a few times. But there isn’t really any emotion attached to it anymore. I know we’ll never be enemies because we love each other and have a child together. He even said I’m still his best friend. Is this dumb and complicated or okay if it seems to be working for us?

I’m 23 and he’s 25 for those asking. We got married at 20 and 22 and dated since we were in 9th grade. Our daughter is 2. We decided to separate because there was constant fighting, it wasn’t just a rough patch. I’m very goal oriented and I have plans of becoming a doctor. He doesn’t really have career goals. He just wants any job that pays decent, plus wanted me to just be a stay at home mom. That’s just one example of many big differences.