Worried sick oral cancer symptoms?

Hi everyone.

I am looking for a bit of advice after worrying myself sick!

Around 4 weeks ago I noticed a smooth painless  bump at the back of my mouth on the upper gum, near my molar. 
The lump comes and goes. Theres no different texture to this or change in colour to this area. 
it seems to appear after I eat or rub my tongue over it too much and goes back down after around half an hour. Sometimes it doesn’t happen at all and its not there for a whole day. It feels quite firm when it appears but completely disappears again after a short time. It is under the gum rather than growing externally and is less than the size of a pea. 

I am terrified this could be oral cancer. I am booked into see dentist in 2 weeks time however would really welcome any advice or opinions. 

i am a 35 year old, female ex smoker 

thank you in advance!