I get this, I think it is sciatica. Got it sometimes before children, but worse now I'm pg for 2nd time. Think it doesn't help lifting toddler DS either.
Things that have helped - sitting on a birth ball, yoga sometimes, also (and this is a little embarrasing) DH vigourously wobbling the offending buttock. I don't ask for that often, as DH generally takes it as a comeon
yes, sounds like sciatica to me too. the sharp pain is the nerve being pinched again, the dull ache is the resulting pain that the body reduces as it gets used to it. as you are getting different levels of pain, it could mean that it is not too far gone or bad yet. it can be caused by the way the womb sits inside you or the ligament relaxing thing but at 13 weeks, its less likely to be this as the ligament thing comes in later I beleive? get checked out by the hospital when you go for an appointment or make an appointment as soon as to check first then go to a good/registered osteopath licenced and insured to work on pregnant women (not all are)