I strongly imagine the charms of your company will go down sharply when you are living with girlfriend's mom, she's doing your cooking and cleaning up and laundry for you in the love nest, and your parents may choose call to the attention of the authorities that your girlfriend's mom, if she is not of age, is encouraging a relationship that's considered less than good parenting. That could cause her mom some grief.
I am also sure you have arranged to pay for and take away your own paid for and properly titled vehicle, and have obtained car insurance on said car, which you, as an 18 year old boy, are paying out the wazoo for, since 18 year old males are not famously known for making good decisions. If your parents bought the vehicle, titled the vehicle, and are carrying insurance on the vehicle, there goes your ride. Without good transportation, the job prospects decline.
Have you finished your education? That you are talking to school counselors leads me to believe otherwise. I might venture a guess that you used to live in Oklahoma, that's where your girlfriend is, and that her mom has said something like, "Sure come on back and you can stay with us and finish high school."
But right now, you are in that super dangerous position that you are old enough to do it, yes, but you are not experienced enough at relationships or at being self supporting to realize exactly what all this would entail if your parents are not in agreement with the program and kick you out without a cent.
In the first place, everybody in the world has to be roomed and boarded, and has to provide a certain amount of upkeep for themselves. Every hot shower you take costs someone something somewhere down the line. Clean towels? Very few teenagers have any conception of just how much their parents are providing for them, or how much it costs for them to be comfortably alive. Rent and food and clothing and electricity and water, electronics, transportation, gasoline, not to mention health insurance. What if you get sick?
Even if this mom is going to pay for everything and keep you up completely, buy you cell phones and new clothes, do your laundry and buy your school lunches, what if your girlfriend decides she wants to break up with you, wants to see other people, etc.? Or if the police visit because of what has been reported, and the family asks you to leave. You're about to be homeless in Oklahoma.
I'm thinking of another possible very bad scenario. I'm not just shocked at your girlfriend's mother, I'm thinking she may be one of those mothers, who, when the daughter has a boyfriend with a family of higher social/economic means (officer's kid as opposed to enlisted family's kid for example) thinks it'd be cozy to have a grandchild with a good provider for the next 18 years, never mind whether there's a marriage or a relationship for that long. Get this girl pregnant now and you're going to be involved with this family, mother and daughter, for a longer time than you've been alive yet. And choices will be made about YOUR life and your future that you didn't plan to make.
Sit down right now and plan yourself a totally self supporting budget for how you will survive (without help!) when you make this move. Assume your parents can't have you thrown in juvie, but they can cut you off completely as far as support. They can take back what they've bought for you. Read about that person who's been kicked out at 18 who is trying to get his clothes and what he considers his personal possessions out of his parents house. Think and plan and try to work this out differently.