Try an insulated air mattress--Pacific Outdoor or Big Agnes. My POE Insulmat Max Thermo (such a long name!), now replaced by the Ether Thermo, weighs 16.9 ounces. The trick is not to pump it up full, but only a little over halfway. I like it where my hip is about 1/2 inch off the ground. Sleeping on a fully blown-up air mattress or inflatable pad isn't much different from sleeping on a rock. You have to experiment as to what is most comfortable for you.

I generally don't sleep too well the first night out, because I'm too excited. After that, though, I sleep just fine unless I've picked too slopey a tent site, where I'm battling gravity half the night.

My worst night's sleep recently was while returning from two back-to-back one-week backpacks. After two weeks out, I just couldn't adjust to sleeping in an enclosed room the first two nights. Not exactly good preparation for a 1000-mile drive home.

The suggestion to avoid sugar and stimulants (this includes chocolate as well as coffee and tea) late in the day is also a good one. But it really sounds as though you need a more comfortable sleeping pad.
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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey