If you can't remember your dreams, it is usually (in my experience at least) because of one of two reasons.
1) The mostly likely reason, you were awoken before you would have naturally woke.
2) The dream was either too illogical, or your concious mind could not accept it.
The first is easy to address, in principle. Go to bed earlier, bin the alarm, and allow yourself chance to wake naturally. If you live with other people this is harder than it sounds, so you'll have to find a way to get your hours in around them.
If you are stressed, you need to address this. Stress messes with your sleep patterns and narrows your thought processes, attempting to force them to fit with what you think they should fit.
The second point is a bit more tricky to address. You need to open your mind. Accept that even if you don't believe something consciously, on some level you might, or somebody/something else might be telling you it even if it is a lie.
I'm not sure yet (because I'm new on this forum) if I'm allowed to share advise about common, legal, culinary herbs that will help, but I know a seemingly innocent little culinary herb which totally unlocks the subconcious and will not only help you to remember your dreams, but will make you wake up in tears, having unlocked everything.