Just to be clear, you're doing 3 sets of 15 reps on every exercise? That's lifting the same thing 45 times, every time, for every motion? If you were working out with the powerlifters I used to train alongside, you'd get laughed at for doing aerobics with the weights.
I'm willing to bet your 40-45th rep of the same exercise is not a shaky, near failure rep either, so I think it's safe to say that you're not exerting yourself to maximal effort during your lifting.
Yes, there are free programs out there. You can also look at the training logs of some of the guys on this site and piece together what they're doing. Or you can pay a little money to a guy like Jim Wendler, get a program that is well liked and respected, and use it forevermore.
As to "how to train," people do know. People here have been training successfully for years. We may not know exactly what works better, but make no mistake doing something in an organized fashion is going to produce better results than picking a rep range, walking into a gym, and doing a few random exercises in that range without a plan.
For the record, I fight at 185-205 lbs (roughly 91 kg). I also bench in the 300s, and squat and deadlift in the upper 400s with PR's in the 500's. I got there by finding heavy things and picking them up until I puked, then eating some protein. It's not rocket science.