Mother in law and husband harassment for dowry and child custody

Sir/ Madam, Once whom i rejected as arranged alliance in 2011 due to dowry demand indirectly has convinced me until Dec 2012 for love marriage with his fake promises about no expectations from me/ my family. But began torturing and harassing from day 3 of wedding. Still i continued staying together by my entire giving 20k salary, working like maid without maid, not allowed to visit parents in same town, yet denied food at home even during pregnancy. After baby boy birth in June 2014, again both my husband and his mother along with my brother in law & sister in law came my parental home, yet again made fake promises to live with me in peace and took me along in Jan 2015. However i underwent same torture daily. On July 24th last month they both took to heights and began very badly abusing my parents and pushing me to wall and slapped me twice after which i called up parents and shifted over night 1am. Now they forefront lie when my father asked. They want to snatch my child for my barren womb sister in law. Our wedding is not registered under govt act. How to stop my husband take custody from my child who is only hope for me to live and look forward to future. Parents are old and heart & arthritis patients, my only younger brother also is a High BP patient. My husband and in laws have nothing but my husbands monthly income to survive on, she gets meager 2,600/- pension and my 35 yr old brother-in-law is jobless idle, feeding on us. As they are not satisfied with my 20k salary and my services not meeting their expectations of my fathers recently retired amount, they got rid of me. Please help me from the severe depression and suicidal thoughts. I want to live for my child sir though i know my parents can take care of my 15 months old baby.