Palpable lump but clear ultrasounds

Hi all writing from ireland. 30 years old, no family history of bc and two children 4 & 1.

During summer I found a large lump in the inframammory part of breast (down the bottom near bra line)

Seen doc who wasn't overly concerned and referred me. In meantime I had private ultrasound which showed normal area of dense breast tissue no need for biopsy. 

I had my public app in October and consultant said not overly concerned but will send u for another ultrasound and have review in 6 weeks. 

I had ultrasound and it was clear. Same woman did it and classed it as normal tissue nothing to biopsy she said.  I was so relieved 

Seen consultant other day and was expecting to be signed off but he wants to biopsy anyway as its still there. He said he wasn't worried and wants to "close the door on it" but I am so anxious ever since and worried sick. Radiology dep wont do biopsy as they dont biopsy normal tissue they said. Awaiting date for biopsy and spoke to nurse who said they aren't worried but it's routine 

Surely after two ultrasounds I should be relaxed?? I have major health anxiety and this is driving me around the bend 

Thanks