Girlfriend pregnant that we can not marry

I brought her back to debut when the two families disagreed and strongly opposed it.

I am 23 years old, living in Hanoi. My girlfriend is 6 years older than me, from Thanh Hoa and has a 4-year-old girl but never married. Although more than 6 years old, but my girlfriend looked younger than me, and I was older before my age, I didn't see much difference. We love each other for half a year, intending to have a baby and then go to marriage. Now my girlfriend is 3 weeks pregnant, we can't get married or get married and we can't be together like that. What should I do, looking forward to receiving the suggestions of everyone.

Tuấn