Achiness on my sides/hip bones?

Aspen436

I'm almost 18 weeks...and definitely showing.  I'm about 5'5 and about 125 pounds.  My bump is getting bigger & bigger by the week...and now I'm starting to feel uncomfortable.  I feel like my stomach muscles are stretching and I've been having some back pain.  Yesterday and today, my sides/hip bones started to hurt.  I feel achy around my hips and it radiates to my lower back but right now it's more on the right side.  I'm wondering if my body is not used to the extra weight pressing on those muscles.  Or is it the baby pressing on one side more than the other.  I'm not sure...has anyone else experienced side/hip pain?  Does anything help relieve the discomfort?  I don't think it's round ligament pain because it hasn't really gone away.  I read on the internet that round ligament pain only lasts for a short time.  Mine has been on & off for two days now.  I hope it's not a kidney infection or something... but I feel it on both sides and I don't have any other symptoms that would make me think it could be a kidney infection.  Any thoughts?