Do you set your alarm for 4.5/6/7.5 hours after going to sleep? If not, try that out, the chance that you remember your dreams after these amounts of times is bigger. Try autosuggestion and motivate yourself as much as possible. Make sure that you know and that you want to wake up when your alarm goes off and that you want to remember your dreams, it should help you to actually achieve this. This way it’s not so much of a big shock/surprise when your sleep gets interrupted in the middle of the night, you might even wake up before your alarm rings.
Here is a good guide for DR: link. I agree with everything mattias said, keep it up and think positively. 