Ay oo, normal talaga yan sa pregnancy lalo na pag tumaas ang weight at posture mo, but two days na ng ganyan plus ang headache, I'd really suggest checking with your OB just to be safe, ha? A few of my mum friends had similar concerns at 18 weeks and ang doctor lang talaga ang makakapag-confirm kung posture lang or something else, so go na lang para peace of mind mo.