From what I have searched online, HPV is usually spread by skin to skin contact so there could be a possibility that your partner may have been a carrier. Also HPV can be with you for days, weeks, months and sometimes years before anything abnormal shows up on a pap smear. You may have contracted HPV from a past relationship or from your current relationship so it's really hard to tell.
The best move you made was keeping follow up with your doctor. I hope this helps some because believe me when you are first diagnosed it's scary but rest assured things will be okay