It sounds to me like you are adjusting to the responsibility that comes with a pet. As long as you are making the choices according to what is best for you and the dog, I can't see anything selfish about it
I used to have two guinea pigs and sometimes it was a lot of work. I couldn't go on longer vacations, had to take them to the vet etc etc. But I loved them and they thanked me with their presence and cuddliness and well being, so it was worth it. I miss them a lot and also I think that taking care of another being than ourselves serves us as a reminder that we are indeed responsible and connected with each other
You will be fine Don't beat yourself up and enjoy your dog's company.