No, they are not trying to help you. They are a government organization merely enforcing bureaucratic regulations. They don't know you personally, so there is no reason for them to help you. You have no personal relationship with them. They are not your friend.
You do not have to answer any questions. That does not mean they won't ask or try to give you a hard time. If they are asking more than a few questions, then that almost always means they are simply looking for something--anything--upon which to act. You might find this hard to believe, but they often want to find something to justify their jobs. If they have no one to pursue, then they would be out of a job. Crazy huh?
There is a now famous viral video by an attorney called DON'T TALK TO THE POLICE. It's a short one and a link is below. This really applies more to law enforcement, but parts of it will apply to you because CPS is also a government organization. I strongly suggest you view it. It is very short.
You have not related your problem, but your wariness suggests to me that any intervention will cause more harm than good. All families have problems. There is no perfect family. The problems will be a matter of degree. CPS will often magnify these problems because this is their history. They often punish parents for drug use instead of finding them help. Separating kids from parents is often more harmful than helpful. Their pat solution often leads to even more problems.
If you have problems that can be worked out, then try to work them out. You have not related your problem, but people are generally better equipped to handle their own problems than the government. It's just a job to them, but it's personal for you. They have no interest in you personally, but rather their interest is in enforcing regulations, many of which are often punitive, dysfunctional, and doing more harm than good.
Unless your parents are trying to kill you or drastically harm you, then either work it out or leave. I suspect from your trepidation that nothing good will come of their intervention.