I had that when I started wearing diapers to bed. My advice: don't push it. Don't think "if I drink a lot before bed I'll be forced to wet my diaper!" It doesn't usually work that way and as you found, it just drives you out of bed to pee. So if you have to go and can't, it's ok, just get out of bed, haul out or shimmy down and pee, and snug back up and get back to bed. Laying in bed desperate to pee just associates unpleasant things with your diapers, and that's not what you want to do.
As for wetting while laying down, as has been discussed in other recent threads, practice practice practice. Find places that are challenging to wet but not impossible, and practice. Work your way up to wetting in bed. You'll get it eventually.