If your parents are open to it you go for renting a place in the same city. You will be close to your parents for support and work and also have some privacy in terms of what you want to do.
Now in regards to you getting bored, I dont think its the city, some people can make friends and socialise anywhere while some cant. You dont need to be with people to spend quality time. Buy console, score some good quality weed, watch TV, all you need are 1-2 decent friends to accompany you in the above.
In terms of your relationship, I was in a very similar position some time back and had to move to my hometown due to parents health issue and leaving my girlfriend behind. We decided to get married rather and got married super young, younger than you are now. An amazing call since it solves 2 points, 1 your girlfriend is with you and 2 you now have a friend to make plans with. You also have now unlocked travelling, travel the fuck out of this world with your SO.