It normally takes a full cycle (approx. 28-30 days) for your birth control pills to take effect. Just because you had sex before they were in full effect doesn't mean you are pregnant. Of course, you could be.
Everybody is different as far as feeling the early effects of pregnancy. I knew I was pregnant from the very night we conceived. However, until I had that confirmed by taking (several) pregnancy tests, it was just a hunch.
My symptoms included a heightened sense of smell, sore breasts (as if I was getting my period), no desire to drink alcohol or coffee, and I spotted which, according to my mother, meant the egg had settled in for the next 9 months.
There's only one way for you to be sure. Get a pregnancy test. It might still be too early for an over the counter pregnancy test to be accurate as they measure the hcG hormone in your body. That's a hormone that's produced when you get pregnant and it increases every day with your pregnancy. It's possible that at this early stage your body just isn't producing enough to measure accurately. You can read more about over the counter tests here:
However, that doesn't mean you should wait to get yourself tested.. Planned parenthood or something similar can offer you a more accurate test.
It's very important not to wait. If you are pregnant, the situation only gets worse with time.