You have to be the dumbest motherfucker if you think you can get in trouble. There is little way to fuck this up.
Just make sure you set up appointments via text message to keep some evidence. Second of all, why would you be worried of her getting pregnant if she's a fucking WHORE who you shouldn't be fucking bareback. If you're not using a condom when fucking a complete stranger and a sex worker of all things, you deserve whatever you get dude. If you have been using condoms and she "magically" gets pregnant, a simple blood test will suffice.
***Check local laws if you're in the USA because some states actually don't give you the right to force a paternity blood test. So yeah, someone smart enough could force you father another man's child.
Also, if you're paying her, and you are a regular customer, she probably won't want to lose you as a customer so she'll be nice to you. If you think you're dealing with a psycho, best way to test it is to go cold turkey on her and don't write or set up anything new. Ignore her when she calls and texts and wait a month or two. If she acts like a desperate psychopath trying to get you to answer her, get the fuck out. If she doesn't even flinch and doesn't message you ever again, she's sane and she just wants your money.
I'm just laying down the real talk because it looks like you need it.