Swollen neck glands after mastectomy

Hello,

I'm torturing myself with worry and panic, and I wondered if anyone had experienced anything similar and could talk me down from my fears.

I had a mastectomy on my left side 4 weeks ago today. I was diagnosed with intermediate DCIS in September, which was a massive shock. I'd never even heard of DCIS until then. 

I got my full results back last monday. The 2 lymph nodes they removed were clear, and they found some Grade 2 cancer had breached the duct walls. They are confident that all is sorted, but I'm on tamoxifen just to be on the safe side.

I started with pain in my jaw after the op. It rumbled along until last week when I got my flu jab and then got much worse. The pain is in my neck and jaw, and my glands are swollen on the side of the op. My glands under my arm are also swelling up and going down depending on their mood. 

I spoke to my GP who thinks it's viral or some kind of inflammatory response. I rang my breast cancer nurse and she agreed with this assessment. I went back into the drs today, and they said if it hasn't gone in three weeks then I must come back in. My body has done this kind of thing in the past, but after everything that's happened in the last few months I'm finding it hard to stay calm. They've reassured me that it's extremely unlikely that cancer is causing this. I can't seem to convince my brain of that.

I lost an Uncle to cancer this year in the space of four months, and an Aunty to breast cancer almost twenty years ago now. As you can imagine, it's making things feel much worse than they likely are. 

Any reassurance would be much appreciated xxx