TS, all men are hamsap. Just the level of craving and self-control are different. For your case, I don't believe gf can curb your 'thirst', since after a few times, you may look for 'fresh meat'... My suggestion is try controlling and/or diverting your sex crave to something else (hobby, preferably something physical, like exercise, gym, sports etc). It may be difficult at first, but with persistence and determination, you should be able to do it.

And, yes, stop supporting illegal business like prostitution.