If so, you need to find mental space. When you observe your thoughts, be aware of the short space between the end of one thought and the start on another. Look for this momentary pause, no matter how brief. Mentally attempt to rest in this space. With practice, you will be able to expand it, and your sense of an overcrowded mind will lessen.
Meditation is the art of opening to each moment with calm awareness.
Try watching your stream of consciousness flowing at full speed. This flow never stops, but you can practice developing detachment from your thoughts. See them as clouds passing across the sky, or even as items on a conveyor belt. Each thought will bring new associations in its wake. Be aware of this, but let your thoughts pass and try not to follow.