It could be contraction. Download the app - contraction timer (in mint green). Time yourself whenever the pain comes back. If the contraction happens every 5 minutes or less, it could be labour coming. If it doesn’t, then it’s false contraction. Just your body preparing for labour. You can let your gynae know during the check up.
At 35 weeks, this one better not wait, please go see a doctor or A&E now. Pain that comes and goes like that needs checking to make sure baby and you are both okay. Don't worry too much, but do get checked out today so they can see what's going on.
nana