Upendo is 23 and lives in Dar es Salaam in Tanzania. She is a young campaigner with Plan International UK's Youth For Change project - a global network of youth activists working with organisations and governments to create positive change for girls.
Imagine what you were doing when you were 11. You had probably just started secondary school, perhaps you dreamed of being a doctor, artist, computer scientist? Maybe you looked forward to the weekend when you could go to the cinema with your friends, go swimming or shopping. It's very unlikely, living in the UK, that you were about to marry someone more than twice your age.
I grew up in a community where most of my neighbours and friends got married young, had early pregnancies and dropped out of school. This is just seen as a normal path for a girl.
Child marriage, sadly, is rife across the developing world. Whether it's fuelled by gender inequality, poverty, traditions, or instability, it can have devastating consequences on the girls who marry young. Across the world, 15 million girls marry by the age of 18 and Tanzania has one of the highest rates of child marriage in the world. On average, one in three girls are married before they turn 18 and in rural areas, some girls are getting married as young as 11.
The consequences of child marriage are serious and they last a lifetime. Girls who marry young will often be forced to drop out of school and abandon their education. They're more likely to have children before their young bodies are ready, causing long-term health complications, and they can also be trapped in an abusive relationship, with nowhere to turn.
I feel proud to have escaped this cycle and can partly thank the day my sister was born for inspiring me to campaign for change on the issue. From the first day I held my sister in my hands I felt a huge responsibility. I wanted to be the perfect role model, not only for her but also for my mum, sister and community.
That's why I am working with the girls' rights charity Plan International UK to stop more girls being violated in this way. The law in Tanzania states that while boys can only get married at the age of 18, girls can be married at 14 years old. We need to make sure child marriage is made illegal and raise the age of consent to 18 years old for girls.
And it is possible, with enough support from the international community; we can get this law changed. In February this year, Malawi approved a bill to make child marriage illegal following a campaign by Plan International UK in which 42,000 people across the world signed a petition in support of the change.
So now is the time to be the change you want to see in the world, and improve the future for girls in Tanzania. I know I will.
To find out more about Plan International's UK's campaign in Tanzania and to sign the petition, visit plan-uk.org/notochildmarriage.