Aww mama, hives during pregnancy is super stressful talaga, especially pag on and off like that! A few of my mum friends had the same thing sa first trimester and nahanap nila eventually what triggered it, sometimes it's just the hormones or a new product, sometimes environment or food din. Since you're observing it carefully na, good idea na i-track if it comes back pag bumalik kayo sa old place, pero I'd really suggest mentioning it to your OB next visit para ma-rule out kung pregnancy-related lang or may specific trigger, especially since it keeps coming back, mas makakatulog ka ng mahimbing once you know it's safe for baby!