Stretchmarks at 11 weeks?!

I am 20 years old and 11 weeks pregnant so I am a young mum and this is my first baby. I haven't been to the doctor/midwife yet as my first appointment is next week. I'm really concerned as my whole tummy is covered in big deep stretch marks already. Is this a sign of twins? I've been applying bio oil day and night ever since I found out at 5 weeks. Help! ):