what can I do for me,I became nervous?

When I married,I was very calm,patient.Now,after 4 years only,I am nervous,I yell,with every occasion.All because my mother-in-low made my life heal.I have a boy 3 years old,and when he was only one month,play with him for one hour,without stop,very intense,strong,and after that he cry,and sleep for two days,and cry in the night a lot.Every time when I try to explain what is happening,she said"it is normal".But every time she left,the baby was ok,and week up only one time in the night.I was diabetic,I was eating little,I don"d sleep,And problems with my mother in low.Always must to disagree with me for everything about my boy.Like when was 2 month,she tell me that I must give him milk every 3 ours,not when he is hungry.To let him cry,and he will use to drink milk with program.And when I do the things in my whey,she argument with me,with my husband,threat.One year ago I close my door and every time she come in to our house,I close the door in my room with key.After three month she left us free,but I am tired now.Nobody do this,the father to my husband,my husband,never dare to disregard her,to disagree with she.Now I don" have anymore problem with her,but I become nervous.What can I do,thanks a lot for any answer.