How do I clear a drain in my bathroom?

Yes that happened to me too years ago. I ended up hiring a plumber that sent the camera down so we could see the pipe. Ended up being old tree roots. Cost a few bucks, no problems since then.

Call a plumber. They can send a camera down to see what is causing the slow drain, could be tree roots, broken drain pipes, etc.

I had my kitchen sink done by a pro with his huge snake and our clog was down in the basement almost out of the house. Perhaps the clog is further than the snake could reach, or you may have something like roots growing through the sewer pipes out in the yard. You may need to get that checked out by a pro.

We had the same problem and it was roots. We had to tear out the old pipe and put new in.