@turquoise-- Yes, English is your second language. Your native language is the first one you learned. Some children do grow up to be bi-lingual though which is probably also the case for you. You can say that you are bilingual if you understand,speak, read and write your first and second languages at native fluency.
It's actually great for people to learn their second language as a child because children are far more receptive and learn quickly. Children can also pick up different sounds and pronunciations and their second language will not have a heavy accent for this reason. Parents know this too and more and more parents are sending their children to schools where second language courses start as early as elementary grades. I even know people who prefer foreign babysitters to help their children pick up second languages.