Dreams occur in a certain stage of sleep, if you aren't entering into this stage of sleep, due to being disturbed, waking up earlier, not sleeping for the same duration of time you may find you are less likely to enter this period of REM sleep that gives you dreams.
Another option is that you are dreaming but you simply aren't remembering your dreams when you wake up.
It likely means nothing at all, other than you either aren't remembering or aren't getting to the stage of sleep in order to dream and remember.
Many people remember their dreams infrequently in comparison to the number of dreams we actually have, but keeping a dream journal and writing any bits of dreams that you do remember in it as soon as you wake up, when they may be fresher in your mind if you do dream but don't remember can help you remember your dreams more frequently if you have them.
In addition to HearthWitch.
If you want to remember your dreams and only remember parts of them or remember nothing at all, it might help (when you are already in your bed) to repeatetly say that you want to remember your dreams. And/or you could write in your dream journal that you want to rember your dreams (also when you are already in bed). It might take some days or weeks, but it might help you to remember your dreams. This way you are going to sleep with this thought in your head and 'order' it to remember your dreams.