so long as its just your feet and legs its ok - its the gravity and pressure so you need to raise your legs so they are higher than your knees and hips to help the fluid drain back (i do this every night now and sit with my feet up on the birthing ball as its higher than my couch)
also in bed i prop my feet up with cushions so they're higher...come morning i wake up and they look mostly normal again...then i repeat it in the evening cos they swell during the day
massage lotion into your legs as if they swell suddenly you may develop stretchmarks, particularly on thighs and backs of knees (i know a few peeps this has happened to)
its if you get sudden swelling in your face and/or hands that you need to seek medical help as it could be pre-eclampsia, but swelling in feet and legs is common
itching isn't necessarily heat rash... itching in pregnancy particularly in third tri is often linked to pre-eclampsia, so if occurs alongside the other symptoms i mentioned which you say you're also getting then you need to get your ass to the midwife or hospital missy!
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