I've had one before and I'm only 17. Just ring the doctors and ask if you can get a smear test, you have a good reason to get one, ask for a female doctor too, it'd probably make the experience more comfortable for you!
I got one because of my reoccurring thrush, haha, lovely, the doctor asked me if I wanted to have a smear test right there and then, I didn't expect to get one, or did I want to wait, I just said I'd have it done then and get it over and done with. It doesn't hurt or anything! And don't be embarrassed, doctors have done it billions of times!