17 day late period!

Queen

So my sister and I have synced periods. She is 15 days late and I’m 17 days. Well she took 2 pregnancy tests when she was 10-11 days late. They showed positive within 3 seconds. I’ve taken 2 tests and they were negative. You ladies think my period may just be messed up because of her? I’m a type one diabetic so I get paranoid about having late periods