First of all, intercourse itself does not cause a delay in your cycle. I can think of no way to explain this impression thinking about the physiology of your cycle.
Second, guys don't always have perfect control, so there needs to be the assumption that there MIGHT have been some pre-ejaculate
that could have been present (that also has a decent concentration of sperm).
If you have a history of irregular cycles AND you were relatively careful, then in all likelihood you are not pregnant BUT you absolutely need to check a pregnancy
test. The earliest that it might turn positive is about 2-3 weeks after conception.
With regard to early symptoms of pregnancy, these might include a small amount of vaginal spotting and/or cramping, breast tenderness, and nausea
I hope this helps!