If I'm 19 years old and got married 6 months ago but my husband went back to England where he is a citizen, can our marriage be annulled or do I need to file for divorce?
You will need to file for divorce. Annulment is not for when there is abandonment or a marriage breaks down. It is for when the marriage was void or invalid from the very beginning, such as because one spouse was no mentally competent when the marriage was performed (and so could not consent to it), or was below the legal age to marry, or was still married to another person at the time they supposedly got "married" again (since you cannot marry person B is still married to person A). But that is not the case here: there is nothing indicating that the marriage was not valid when entered into, which is why you would need to divorce.
Your situation does not qualify for an annullment as it was not void or voidable (each state has specific requirements for this). Accordingly, you will need to file for divorce since your is a case of abandonment or break down of the marriage.