First Haematology Appointment

Hi all. 
 

im a 26 year old male who's had near constant back pain for the past year I've got my first haematology appointment this week and I'm very nervous about what it is, what they do etc. 
 

ive been referred as my doctor is very unsure of what's happening and as I've lost 8 pound in a matter of weeks. 
 

has anyone got any experience of these type of appointments and what do they mean? 
 

thanks, Luke x