Ahh pregancy worries

Hi im 19 and i slept with a lad about 3 weeks ago and i still havnt came on i was ment to come on about a week after i slept with him .. And now im getting weird signs ... Im getting pains in my stomach not sevear but bad enough ... I also feel bloated and very gassy .. Im also getting discharge and i cant be to sure but im not feeling up to my normal food and feeling tired i dont know what to do if theres anyone out there that can help it will be great thanks