mammograms - worried

I am 38 and recently had a mammogram due to breast changes. Came back clear. Now I keep hearing stuff about people saying mammo’s didnt show up their bc and its scaring me again. I havent got a lump so would it only show bc that is a lump? I did also have an ultrasound just of my left breast as that was where the pain was and that just showed swollen glands and have since been taking epo daily which is working. So unsure though of how much I can rely on mammo’s?