i started having exactly the same bites, at pretty much the start of my pregnancy.
started off as small red bumps,which grew into (insanely) itchy white lumps & would then stick around for anything up to a week, and would constantly itch. they looked like hives. i was getting them everywhere - legs, arms, necks, back. and i was coming up in them all over the house & even at work. because of this, and the fact they weren't in lines, i completely ruled out bed bugs, they definitely weren't flea bites (as i know what they look / feel like).
the other half had not a single bite, so i went to the dr and they said it was an allergy i had developed since being pregnant. kept a food diary, but there was no pattern at all.
the 'hives' were getting worse, and i have had them constantly for five months. obviously cant take any antihistamines, so was relying on calamine lotion & tiger balm to take the itch away. i am covered in scars where i have scratched them (often in my sleep!) & they have bled more.
then, last week, DH found some blood splatters on his side of the bed, although still no obvious bites on him. he pulled the bed apart, literally unscrewed it... and lo & behold, hiding in all manner of tiny crevices were BED BUGS (heave). not loads fortunately, maybe 20 max. but enough. he systematically squeezed everyone, we hoovered the mattress, steam cleaned the carpets & washed all the bedding & curtains at 90 degrees.
since then? not one single bite (HURRAH!). it turns out bed bugs dont always bite in lines. some people are more allergic to the bites (hence why i was having a reaction & DH wasn't) & sometimes pregnancy can make you even more sensitive reaction-wise. and sometimes, the reaction doesnt develop until a log time after the bite - which could explain why you are coming up with them even when you are not in bed.
ever since that fateful day, we have checked the bed frame & mattress daily, and no sign of anymore as yet.... if we find anymore, we will get the exterminators in.
still makes me cringe thinking of all those horrible little critters feasting upon me for the last 5 months!