Early pregnancy symptoms?

I'm 16 & I've only had sex once and ever since I've been completely paranoid and stressed because I'm constantly thinking "what if I'm pregnant". I had sex for the first time about 3-4 weeks ago and had my period 4days ago and it was quite heavy as usual and it lasted for six days. I just really want to find out what the most common symptoms are in early pregnancy so I can at least get some peace of mind hopefully.. I don't really have any way to get a home pregnancy test on my own so I'm pretty much in the dark..