Worried, any advice?

Good evening everyone, 

I'm looking for someone to ease my worries. I'm so worried. I'm 25 and a mother of 3.

My left breast and armpit started hurting October 2020. Dec 2020 i book appointment. No lumps but gp felt "thickening" and referred me for an ultrasound. At the time I never asked what thickening meant and just went along to my ultrasound. (I still don't know what thickening means, if anyone could explain that would be great thank you). I go for my ultrasound and the lady felt my breasts before the ultrasound and agreed it feels thicker tissue than the right breast. The ultrasound revealed nothing and that all is well. Great news! I'm prescribed some naproxen by GP for the pain and go on my merry way. I forget about it, the pain eventually passed months later.

The pain is back now and has been for about 2 months. An achey lightning type of pain. When I press my breast certain areas hurt and its like I can press exactly where the pains are.. like pin point the exact bit of breast tissue that is hurting. My armpit  hurts too. I want to go Back to the gp but don't want to waste anyones time. I cannot feel a lump its just pain. I had a chest x ray In January this year due to having pneumonia,  would they have found something on that if there was anything sinister going on? 

Thanks again 

Take care

Jess xxxx