What could this be in early pregnancy?

i took a hpt last night and tonight and got positives on both....faint line because AF is not due until tomorrow.....well i dont kow if anyone else has had this i get this feeling in my stomach its hard to explain its like sore on the inside like so,ething is hitting the inside....not like cramos but just sore......i got this early on when i was pregnant with my son....i probably got it like a couple days after my period wa late and then i started to spot.....culd it just be from implantation??? i mean that is the only thing i can think of....has anyone else had this and if so what did your doctor say about it?