To be refused us visa four times means there is a fundamental problem with your application. Now you need to review all your previous applications carefully to detect where the problem is reoccurring.
For instance you said you were denied the third time because you do not have a strong family ties in the States. Having a strong family ties in the States can actually be a reason for the denial because you will seen as an intending migrant. You do not need to have strong family ties in the states but a strong family ties in your home country plus a professional and social ties to your home country that will compel you to return after your visit to the States. You need to demonstrate this during your interview as you 'may not" be asked to produce documents to back up your ties to your home country even though you have the documents. Documents are to assist you but are secondary to the consulate officials because visa approval are strictly based on the oral interview and the information in your DS-160 application form.
Your application history may be complicated now. So you need to re apply with a compelling and detailed argument in your favor to turn the denial around for you. There is a section in the DS-160 form were you are asked if you have ever been denied a US visa. You answer yes. Then a follow up paragraph will pop up asking you to explain. This is where you pull the trigger to get your visa. Whatever argument you put up there will determine your visa approval.
You may need someone with the knowledge to help you with that compelling argument. I have been able to turn a lot of such cases around for applicants in my neighborhood.