My 2p worth.
Start with a half hour massage with an HE. Do that a few times till you're really comfortable with it, then try a B2B.
When, (and only when), you feel ready move on to a decent massage parlour like the Studio and choose someone with good reviews here. Maybe just get sucked off on a first go, (or go's), then move on to FS when you're ready. No rush, take your time, really enjoy the journey.
Try talking to civi girls too. You don't need to really fancy them, in fact it may be better if you don't. I then doesn't matter if it doesn't work out, you can just move on to the next one. The goal is to get yourself where you want to be whan you meet someone you really like.
If the problem is being overly stressed and then failing to perform ... then do whatever you can to take the stress out of the situation. Consider it training.
An SP is getting paid for her time. She doesn't mind if it's not a great sexual experience for her.
Just take it easy, you'll be where you want to be in no time.
As I say, just my opinion. Good luck.