I can see how this would make life difficult. I have my own OCD habits that make life hell at times. The best way to defeat it is to push through and let the thoughts come. Eventually, you'll see that good and bad things happen, no matter what the number, and even with 13, most likely, nothing bad will happen.

Superstitions are hard to break, but if you pay attention, numbers don't cause things to happen or not happen (except maybe the lottery ). You have to try to force yourself to not add up numbers and just trudge through entrances and exits. It isn't easy, but it can be done. I had to stop focusing so much on numbers. I still do it sometimes, but not as much as I used to.

You say you take medication; do you have a pdoc? A good psychiatrist or psychologist can help you in fighting those thoughts. Perhaps a change in your meds is needed to ease those thoughts. My medication makes it MUCH easier to deal with my OCD. I still have a lot of depression and frustration, but it's still better than what it used to be. I hope you can find the help you need.