3 weeks late on period had watery pink fluid when wiping only happened once, pain during sex and soreness the last week any ideas what this could be?

Check a pregnancy: test to see if you are pregnant, especially if your periods were regular then whether pregnant or not you need to see your physician.

Delayed or: missed period provided that you are not pregnant. Do a pregnancy test. If it is negative then you are probably having an infection going on. By the way an infection can cause a delayed or missed period. To give a visit to your gyn for an exam would be a good idea if the pregnancy test is negative .