Does it feel kind of like being weighed down? Almost like if you have a block of bricks on you and you're going to be crushed?

If so, this is also a problem I've had for a long time while trying to project. I've heard many pieces of advice such as getting more used to meditation, but I'd definitely rule out health factors first.

I had the issue for years, and only recently discovered that I have an inflammatory issue with my ribs/chest that comes and goes, but can make breathing feel weird when lying on my back. (I'm not trying to freak you out here by saying you definitely have something similar, but it's always nice to be on the safe side, especially where pain is involved.)

I don't know how to phase this correctly. But their is a difference between separation and just getting up. You can always check to see if your body was left behind. But believing you got up normally can help solidify your astral form. Also it might help knowing for some people, doing less requires less breathing.