Talk to your doctor, be honest about your sexual history and current situation. It made sense for me to get the vaccine, but may not make sense for all, or at least not make sense enough to be approved by your insurance.
When I asked her about it, since it seemed like her risk of contracting HPV would be very low, she mentioned she was doing it to mitigate the risks she faced as a woman who was barely 5 feet tall and didn't weigh 100 pounds soaking wet. She said she already has to keep her head on a swivel against the possibility of assault, and she'd really rather not have to worry about a virus that could cause cancer in addition to that risk.
I had the privilege of not ever having had to pay much attention to the risk that my current sexual situation might change without my consent, but it was sobering to be reminded that was something that she had a reason to have on her radar.