I have tried everything, this is what is working atm:
When you feel sleepy on the sofa that is probably the time to go to bed, don't stay on the sofa. Whatever time it is. You might wake up again later but it doesn't matter, you will have banked some sleep.
Make the bedroom cool (if poss), dark, uncluttered. Quiet music or talk radio if it helps.
If you're not falling asleep in a reasonable time, go back downstairs and find something to do, tidy up, read or do some soduko or puzzles. Word puzzles will stop your brain dwelling on other things. Catch yourself when you feel sleepy or start yawning and head back to bed.
Rinse and repeat.
Train your body: Bed is for sleep. Sofa is for reading and puzzles.
(Plus the usual, milky drink, magnesium, tetley's bedtime tea, fresh air and exercise in the day, bright light in the mornings, and less carbs in evening meal as that makes me fall asleep on the sofa.)
Good luck!