Needing help!

Okay so lately I've been getting both positive and negative results, used different brands aswell to be on the safe side but mostly use first response, I did do a clear blue and came up negative but I think I tested too early, the lines I'm getting have been very faint though, I've been getting headaches, stomach cramps, dizziness, backache, and nausea, if they're any signs, I'm really stuck on what to do, If it is positives then I would've concieved 2-3 weeks ago PLEASE HELP ME!