When I was 5 weeks along I was having some pains on my lower left side, but I was also diagnosed with an endometrial cyst 10 months earlier...so I'm assuming its still there and just causing pain.
I found a lot of stretching and moving down there that early on, so I think its all normal.
I havn't felt the pain since and I'm almost 11 weeks along...but I know the cyst is still there...
Perhaps you could have a cyst on your ovary? They are harmless during pregnancy for the most part!