Painful stomach and back cramps with nausea. 35 weeks pregnant.

I’m currently 35w5d pregnant. Today I was out having a shopping day with my parents when my back and stomach started to ache; I figured it was all the walking so took it easy for the evening.

It’s been a few hours and I’m getting very bad menstrual like cramps every 8-9 minutes lasting approximately a minute and a half and with them lower backache/pressure and just feel sick.

I’m pretty sure I’m not in labour as everyone says you’ll just know when you are but what else could it be? I’ve had Braxton Hicks for weeks but not like this!