I think I'm pregnant but not sure.....

So for about two maybe three weeks I've been experience nauseasness and feeling very weak. I've also started experience lower back pains and my last period started out the first day normal then turned into a slight spotting. Me and my husband have been tryin for some time now and several fertile days last month we had sex so am I freakin out thinking about it to much or could I really be pregnant?? Help please!!!