What you can say when they ask you what you need help for is something like this:

"I've never sought help before but I have some sexual abuse in my background and I need help dealing with it."

Those words may be hard to say but, trust me, they will not be surprised to hear them and you will not be the first person to say them. If you feel that you are having to say them in front of a lot of people, ask them if you could tell them in private. Or if it's over the phone, it should be ok.

Everything else they ask you should be in private. If not, complain to them and ask for a more private setting. Tell them you are not comfortable dealing with private information in front of nonprofessionals.

Also, is there someone you can take with you for personal support? A trusted friend? A relative? They could go with you and wait in the lobby? Some city and/or county services offer home visits, too. All you need to do is make a phone call and there's a possibility that someone could come to your home.

Please make a phone call and see what you can find out. You deserve this help for yourself. I know it's hard. Believe me, I know. I've been through it. But you are worth it.