My period is 3 days late and it feels like it is coming any second. Am I pregnant?

I had sex with my boyfriend on the 10, 11, 12, 14 and then again on the 18th day of my cycle. I usually have either exactly 25 or 28 day cycles it has never been anything more/less than that. Now, my period is 3 days late, my breasts are sore and I have that feeling that my period is going to come any second. I had really bad cramps around the 20th day of my cycle which I believe could be implantation cramps, and I only saw a very small amount of blood around that time. Any thoughts?? Thank you to anyone who helps :) xx