What are the chances of getting preg by precum on fertile days? i'm 2 days late and have not experienced any pms which is strange.

Good to great chance: Pre-ejaculate has lots of sperm in it. Not as much as the rest, but it only takes ONE. Take a pregnancy test. Follow the directions. Repeat in 1 week if no period and still negative. If you did not use protection, consider checking for sexually-transmitted diseases (unless in a monogamous relationship over a year). Pregnancy can be the least of the dangers of unprotected sex.

Non-zero: I doubt anyone can tell you an exact %, but we'll all tell you it's possible. It's not nearly as high as if he ejaculated into you, but... So, you'll need to do a pregnancy test and if it's positive - consider your options. I'd recommend a follow-up blood test at a doctors/clinic where yu can get good information on your situation. If it's neg this time, take it as a warning - use protection!

Chances are good: As a young woman, your fertile days combined with any sperm could lead to pregnancy. I would do a home pregnancy test with your first urination in the morning to see if you are pregnant. If your period does not come in a week, I would retest or go to your doctor for blood pregnancy test.