It could well be due to a water infection and your body generally adjusting to getting ready to carry your growing baby.
If the pain gets any worse, you feel very unwell or you get a fever, bleeding or any pain in your shoulder then go straight to casualty.
If you're still worried you could ask for a referral to an early pregnancy unit and if there is any concern then they can examine you to feel if there is any wrong and may do a scan to check whether the pregnancy is progressing normally and in the right place. Even though the pregnancy is early it could be possible to do an internal scan.
Make your concerns known to them and they can act accordingly to put your mind at rest. Also let them know if you have any "risk" factors such as problems (or operations) with your ovaries or other pregnancy related bits such as PCOS or Pelvic Inflammatory Disease, a previous ecopic pregnancy , have had IVF or had any previous terminations especially you had an infection afterwards.