Lump found under left breast, sits directly on ribcage

For the past couple of weeks I’ve felt an uncomfortable sensation underneath my left breast on my ribcage but I’ve either just thought it was the position I was sitting or I had pulled it in the gym, I rarely wear bras and I wore one yesterday and it felt even more uncomfortable than usual. I just thought it may of been my bra morphing into an uncomfortable shape so I wore it again today and it felt even worse than the day before, underneath my breast began to get even more uncomfortable so I began to feel around it and I can feel a large distinct bump directly underneath my breast. It’s not painful but extremely uncomfortable and I find it hard to lie down or sit up without feeling any sort of comfort. The lump feels tender and doesn’t hurt to touch, it’s not necessarily visable but you can feel a large lump. My mum and dad have previously had hernias and they both think it could be that, I’m begging to stress out and panic about it. I’m going to book an appointment with the GP tomorrow.