Pregnant?

I suspect I'd only be about 3 weeks if I was pregnant, I've been really tired lately and my stomach has gone all hard and looks like it's filling out (like I'm slowely getting fat) but only my stomach area, I'm on the pill but it was recently changed so I'm not sure if that's caused any of this? I took a test and to me it looks really faint? I'm not sure if that's a definite no or not, is it possibly I still could be seeing as I'd only be roughly 3weeks this weekend coming.. I'm not super worried but I'm just not sure when the best time to test is..