Could you be thinking of Trazadone? (Deseryl) which yes, does help to aid falling asleep? Tramadol is in fact a pain med.
Last week I posted here asking about Tramadol's addictive properties and the responses I got were a little surprising and a bit worrisom for me~Though most doctors say it is not addicting, if you do a search here you will find lots of people whose life has become miserable taking them and or "stopping taking them". Though, I am currently on a low dose, I still get a sense that quitting them will not be easy for me. sigh. I was also told about the risk of seizures, which would be increased for me since I was also taking an SSRI.
Rather then risk seizure, have you considered asking your dr. to prescribe something maybe a little stronger to control your pain, where you would need fewer per day? I think needing 16 Tramadol to relieve your pain sounds like you need better pain control/management.
I hope this helps.