Give the GMAT only if you think you are confident. This is atleast a 7 days before your G-day. If your G-day is fast approaching, you don't have to panic either. And no need to give-in. Go give the test, and give it your best shot, at least you should feel satisfactory.
Move on with life as it comes, you get the position with the PE-firm, you want to take it, take it. You wanna leave it, leave it. Life goes on, and GMAT always and always gives you many many chances. A failure at GMAT once is just a learning curve, you'd actually know how to do it better the next time. It is absolutely immaterial how many times you take the test, of course, 4 and beyond might start seeming that there is repeatedly something going terribly wrong.
You are just 22, don't plan. Just go with the flow. Typically, an MBA degree carries much weight only after a real-time 5 or 6 yrs of experience out there, in the corporate world. And GMAT scores are valid until 5 years, exactly on your test date, so you could actually take 2 years off if you wished to. Just make sure, you don't waste time or money with bad decisions. If you have a potential situation that let's you earn, better make some bucks first.
I am AWESOME and it's gonna be LEGENDARY!!!