My first question would be WHY? What is your motivation for using English with your child? If it is primarily because you are worried that your child will not be able to reach a decent level of English without your extra input, I would tell you not to worry.
Nowadays, we all have far greater access to resources in English for children. There are so many other things you can do with your child to help them. Why don’t you watch one of their favourite cartoons in English with them, sing together, read together, take them on holiday somewhere English speaking, sign them up to activities in English with children their own age…. Why would you want to sacrifice the chance of communicating to your child in your own beautiful and rich language?
As a mother of two young children, I wouldn’t dream of speaking to my girls in any language other than my native language. We call it mother tongue for a reason. In my opinion, language is much more than a simple means of communication. It is a part of our identity and it allows us to form emotional connections. A fetus in the womb hears their mother speaking when they are just 15 weeks old and one of the first things we do with our babies is to sing lullabies. How natural would it feel singing lullabies in English or mimicking animal noises that are very different to your own language. Woof or guau? No matter how good you may be at English, conversing with a toddler may seem easy but how would you feel about potentially dealing with a teenager’s deeper and more difficult issues in a language that is not your own?
You may think that because I am English, it is easy for me to say all this but I really don’t think that is the case. My husband is Italian and before having our first child, he had pretty much decided that he would speak to our daughter in Spanish as it would be more “useful” for her than Italian as we live here in Spain. In the end, I managed to convince him to speak to her in Italian and to this day he doesn’t regret my doing so. She is half-Italian and the language is part of her identity, her emotional connection with her babbo and how she connects with her grandparents and family in Italy. It is so much more than language.
Summing up, I would tell you not to miss out on speaking to your child in your native language, whatever that might be, and by allowing your child to do fun things in English as they grow up, rest assured they will grow up with a love for English too!