How to detect a cancer? Me overthinking.

My mother is suffering from pain between her chest and stomach from last few months. It goes and comes back. But few days back suddenly der felt a lump or tumor kind of thing(3-4) so we went for a checkup nd d doctor advised for a xray which came out be perfectly fine. Dey gave her some pain killers which eventually reduced d pain but it is not completely gone nd it keeps popping back. Though d lump kind of is also not visible after d medication. But i fear if it is something more serious. I have done a lot of research from my side and i fear of cancer. Doctors just recommend xray nd give some medicines and just ignore d seriousness of it. I  would be very grateful if anyone here can help me with how we can come to a conclusion dat y is it happening nd how to detect a cancer or if der is anything more to it. Or is it just me overthinking.