Lump in neck

Hi everyone just wondering if anyone has had similar..I've had a lump in my neck right next to my collarbone in the centre for about 3 months which has started growing. I was sent for an ultrasound and they couldnt find anything but there is a lump they can see and feel. They said my thyroid was fine and normal so now I'm so confused what it could be I've had no answers and the worry is keeping me up at night. Thanks for reading xx