@abbie I was like this until about 10DPO , it does get better (and all of a sudden!) but I sympathise , its an horrible feeling and can cause shoulder blade tension thereafter, best help I found was to force your back to sit up straight in a very upright chair (like one round a dining table, just for 15 mins or so even) , it made me so much worse laying back all the time plumped up by pillows, hope it eases very soon for you xx