What are the common causes and symptoms of low Progesterone?

Causes include stress, some medications, menopause, poor nutrition, insulin resistance and high estrogen.

Symptoms can be misleading in many cases as symptoms can also be shared by other conditions.  The more specific symptoms would be problems such as polycystic ovarian syndrome, endometriosis or uterine fibroids.

And does Progesterone need to balance with other hormones? I.e. could high estrogen or something affect Progesterone?

Yes, there is a balancing act that goes on not only with estrogen, but also other hormones, neurotransmitters and peptides.  This is one of the reasons I am against the use of the so-called "bioidentical" hormones such as progesterone.  They can trade one imbalance for another.

What are the ways to boost it if its low?

Be careful with trying to raise progesterone levels.  Many of the symptoms of progesterone