Bernie's asked me to chime in on this one since I'm a bit more in touch with the female side of things than he is (I am a girl, after all) and I've had some personal experiences with the questions you're facing right now.
I hope I can offer some useful information, but I have to say right off the bat: absolutely no one is going to be able to answer the question you're really dealing with right now, which is whether or not you're pregnant. All you can really do is wait. The early symptoms of pregnancy are frustratingly similar to common pms - sore breasts, fatigue, headaches, cramps, and even a bit of bleeding (though that's quite rare). At the point you're at, 4 days post possible conception, it's unlikely that you'd be feeling too many things, since the fertilized egg would still be traveling through your tube and not triggering too many hormones yet. Again, you really just have to wait. I've been there, and I know that it's hard, regardless of the answer you're hoping to get.
As for pregnancy tests, there are some that claim to be able to tell you 5 days before you've missed your period, but I've heard of a lot of false negatives with those, so you would do best to wait until you've actually missed your period by at least a day.
In the meantime, the thing to do is to take good care of yourself, and try to stay happy. Get lots of sleep, eat well, drink lots of water, and avoid alcohol, cigarettes, sushi, sandwich meat, and anything that might have gone bad. Bernie could jump in here with some good advice on what sort of yoga to do to stay as healthy and relaxed as possible. I think I've heard that you should avoid strenuous twisting, but he'd know much better than me on that.
I hope this helps. Take good care.