My last period was April 10. I'm 4 to 5 days late, what are the chances of me being pregnant?

Depends on whether you had sex around the time you would have ovulated. If so, there would be a chance, if not... no chance at all.

Sometimes periods are just off. If you are usually quite regular, as in every 29 days or something similar, try a test if you feel pregnancy is a possibility. You could always give it another week or so and see if your period is just late. You might even skip a month from time to time.