I work and support my family. My husband does not support me I have three children already. Am I justified in having an abortion as I have recently found out I am pregnant.

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

According to the preponderant opinion – that which we choose - aborting what is in the womb is not allowed even if it is in the stage of sperm and the soul (life) has not been breathed into it yet.  It is permitted only if there is dire necessity.  The reason mentioned in the question is not a valid reason.  Allah has guaranteed the sustenance of every living thing.  Allah Says (interpretation of meaning): {And kill not your children for fear of poverty. We provide for them and for you. Surely, the killing of them is a great sin.}[17:31].  Allah also Says (interpretation of meaning): {….kill not your children because of poverty - We provide sustenance for you and for them;…}[6:151]. 

Know that a mother is not responsible for spending on the children.  But the father is responsible to bear the expenditure of his children.  Therefore, if the children are from this husband then he is obliged to spend on them, if they are from another man then it is likeable for your actual husband to spend on them above all if they are orphans.

Allah knows best.