I noticed a lump between my breasts but it feels more on the right side, my mom will schedule me a ultrasound, but my period is about to come any moment and my boobs are really in the pms and hurt.. So I'm wondering if i should wait until my period comes and they loosen up? Because they sre too painful to be touched and I can imagine having an exam now....

Will it be too late to wait because I have this lump? I've read 90% of lumps are not cancer and I'm a teen so im literally freaking out..