no TRV needed but concerned

[mm]

Hi I`m a Slovak Republic citizen and would like to visit my boyfriend (who is a Canadian citizen) in Canada for a few months. I don`t need a TRV, have the letter of invitation, a return flight ticket and some money on bank account (3000 CAN) BUT not much ties back home (19yrs old, just finished high school)..does this mean the immigration officer at the airport could deny me the entry?
is it all up to them or can I get some kind of permission for entry down here, to be sure things will be okay before I actually get there?
is it to my disadvantage that I`ve already been to Canada in June (although returned on the right date)?

thank you soo much for your reply :)