Pregnancy symptom anxiety

 I've got PCOS, IBS, I have no thyroid, and I have a slew of other medical problems as well. Because of all of that, I'm constantly missing periods and having symptoms similar to pregnancy. It's to the point that people have even commented or joked about me possibly being pregnant. Unfortunately, I am extremely anxious and in no way shape or form do I want to get pregnant any time soon. With some of my issues, getting pregnant would be hard in the first place. Plus myself and my SF  use multiple forms of birth control. But yet, every time I'm late, or every bit of spotting, or with every Pcos or IBS flare up, I always start the viscous cycle of thinking I'm pregnant even though it's extremely unlikely. I've even had negative HPT's before and still thought maybe they were wrong since I know that happens to people sometimes. What can I do? Any advice from anyone who has maybe felt the same way? I need a way to stop thinking I might be pregnant 24/7.