devotee013

I think you need to give it more effort.
The aim is to remember multiple dreams every day.
Writing the dreams isn't the important part - you need to recall them. You can go over them in your head, you can draw them, create a mental map, voice recording, write them... whatever you want. Personally, I think writing helps with putting things (vague pictures, feelings, memories) together and making sense of them. The work you do putting your dream memories together is what counts.
You say you sometimes forget to write your dreams. Every time you wake up (in the morning or during the night), your first thought should be: "What was I dreaming about?" Stay in bed for a couple of minutes, start with your last memory and work backwards.
Also, think about your dreams during the day. Be obsessed with your dream life. Think about your dream characters and locations, look for connections between your dreams, find what's special about your dreams, study them. If you are into some kind of art, create art inspired by your dreams. Relive your dreams in your mind and daydream about getting lucid in them. Notice your dreamsigns and tell yourself that the next time you'll see them, you'll realize that you are dreaming.
Stay consistent in this work. Lucid dreams will come, sooner or later. Until that time - enjoy the game - which is dreaming.

do the words mean anything to you?

Yes it is okay to write only 3 words down in your dream journal, assuming you can't think of more details. Sometimes just writing a few words down spurs more memories and details to surface. It is better to put anything than nothing at all.

Your goal should be to start with 3 words, and build from there. After writing 3 words, see if you can write more the next night, even if it's just 4 words. If you blank, instead of trying to write down a narrative, write simple descriptions. Example: Setting. Person remembered. Action. Etc. So you could start with : My house (setting). Sister (person). Screams (action). Then later, fill it in with more details, if you can, during the day. You can convert that to : "I was in my house at night when my sister rushes in saying she heard someone screaming." Etc.

I do believe in writing over just trying to remember in your head. By writing, you are putting forth a certain amount of effort that tells your subconscious that dreams are worth remembering. It strengthens your intention to recall your dreams, and intention is everything. Your recall will improve if you write down all of your dreams and fragments.

BTW, when you say some night you don't dream, that is a common misconception. Every night we dream, we just don't always remember them. We usually have 3-5, or even more, dreams a night. Good luck!