A couple more ideas for learning chords that are physically difficult:
- put on a capo, and try the chord again. The capo will lower the action and make the frets closer together, so it's not as much of a stretch sideways. (But if you capo too far up, the neck starts getting significantly wider, so you have to find a balance). Then when you can play it with a capo, try it without.
- try putting down the fingers of a chord in slow steps, making sure each finger is placed as well as possible, with enough pressure to do the job but no more. Vary the order in which you assemble the chord - sometimes "anchoring" the top strings first, sometimes the bottom.
- my current strategy: I put medium strings on my guitar, which made certain chords and hammer-ons much more difficult at first but is beginning to feel normal. And my plan is to put on lights next time I change strings, so that everything will suddenly be very easy. I'll let you know if this works.
Oh, and if you're going to play your guitar in bed, don't use a white pick. It'll get lost in the sheets.