If you had a single surge and you are pretty sure of when you ovulated, putting you at 13dpo today, then it's likely your period about to start.
Your luteal phase doesn't usually vary, at least it won't by much, maybe a day or so. But the time between your period and ovulation can vary hugely, which is why temping can be so helpful. If you want to know with more accuracy then I would suggest buying a cheap basal body thermometer from Amazon and start temping from CD1 onwards whilst using OPKs. It doesn't have to be solely a ttc thing, many use it to track their cycles better, to see if there are any potential hormonal problems, and also to prevent pregnancy. Some will use it in order to have safer unprotected sex (which can only be achieved realistically if you know your cycle like the back of your hand), because after charting for a while and tracking all fertile signs, they can have a pretty good idea of the times to avoid having unprotected sex if they don't want to be pregnant. So, it can help for a variety of situations, and certainly wouldn't be unusual for someone who isn't ttc to do